[pkg/pdatatest] Ignore span timestamps (open-telemetry#27798)

**Description:** 
Support ignore timestamps in span comparisons for pdatatest.

**Link to tracking Issue:** 

open-telemetry#27688

**Testing:**
make chlog-validate
go test for pkg/pdatatest

**Documentation:**
Add usage for `ptracetest.IgnoreStartTimestamp()` and
`ptracetest.IgnoreEndTimestamp()`

.chloggen/pdatatest-ignore-span-timestamps.yaml

@@ -0,0 +1,27 @@
+# Use this changelog template to create an entry for release notes.
+
+# One of 'breaking', 'deprecation', 'new_component', 'enhancement', 'bug_fix'
+change_type: enhancement
+
+# The name of the component, or a single word describing the area of concern, (e.g. filelogreceiver)
+component: pkg/pdatatest
+
+# A brief description of the change.  Surround your text with quotes ("") if it needs to start with a backtick (`).
+note: "support ignore timestamps in span comparisons for pdatatest"
+
+# Mandatory: One or more tracking issues related to the change. You can use the PR number here if no issue exists.
+issues: [27688]
+
+# (Optional) One or more lines of additional information to render under the primary note.
+# These lines will be padded with 2 spaces and then inserted directly into the document.
+# Use pipe (|) for multiline entries.
+subtext:
+
+# If your change doesn't affect end users or the exported elements of any package,
+# you should instead start your pull request title with [chore] or use the "Skip Changelog" label.
+# Optional: The change log or logs in which this entry should be included.
+# e.g. '[user]' or '[user, api]'
+# Include 'user' if the change is relevant to end users.
+# Include 'api' if there is a change to a library API.
+# Default: '[user]'
+change_logs: []

pkg/pdatatest/README.md

@@ -24,7 +24,7 @@ func TestMetricsScraper(t *testing.T) {
 	require.NoError(err)
 
 	require.NoError(t, pmetrictest.CompareMetrics(expectedMetrics, actualMetrics, pmetrictest.IgnoreStartTimestamp(), 
-		pmetrictest.IgnoreTimestamp()))))
+		pmetrictest.IgnoreTimestamp()))
 }
 ```
 
@@ -59,6 +59,7 @@ func TestTraceProcessor(t *testing.T) {
 	expectedTraces, err := readTraces(filepath.Join("testdata", "traces", "expected.json"))
 	require.NoError(t, err)
 
-	require.NoError(t, ptracetest.CompareTraces(expectedTraces, actualTraces))
+	require.NoError(t, ptracetest.CompareTraces(expectedTraces, actualTraces, ptracetest.IgnoreStartTimestamp(), 
+		ptracetest.IgnoreEndTimestamp()))
 }
 ```

pkg/pdatatest/ptracetest/options.go

@@ -5,7 +5,9 @@ package ptracetest // import "github.com/open-telemetry/opentelemetry-collector-
 
 import (
 	"bytes"
+	"time"
 
+	"go.opentelemetry.io/collector/pdata/pcommon"
 	"go.opentelemetry.io/collector/pdata/ptrace"
 
 	"github.com/open-telemetry/opentelemetry-collector-contrib/pkg/pdatatest/internal"
@@ -126,3 +128,47 @@ func sortSpanSlices(ts ptrace.Traces) {
 		}
 	}
 }
+
+// IgnoreStartTimestamp is a CompareTracesOption that clears StartTimestamp fields on all spans.
+func IgnoreStartTimestamp() CompareTracesOption {
+	return compareTracesOptionFunc(func(expected, actual ptrace.Traces) {
+		now := pcommon.NewTimestampFromTime(time.Now())
+		maskStartTimestamp(expected, now)
+		maskStartTimestamp(actual, now)
+	})
+}
+
+func maskStartTimestamp(traces ptrace.Traces, ts pcommon.Timestamp) {
+	for i := 0; i < traces.ResourceSpans().Len(); i++ {
+		rs := traces.ResourceSpans().At(i)
+		for j := 0; j < rs.ScopeSpans().Len(); j++ {
+			ss := rs.ScopeSpans().At(j)
+			for k := 0; k < ss.Spans().Len(); k++ {
+				span := ss.Spans().At(k)
+				span.SetStartTimestamp(ts)
+			}
+		}
+	}
+}
+
+// IgnoreEndTimestamp is a CompareTracesOption that clears EndTimestamp fields on all spans.
+func IgnoreEndTimestamp() CompareTracesOption {
+	return compareTracesOptionFunc(func(expected, actual ptrace.Traces) {
+		now := pcommon.NewTimestampFromTime(time.Now())
+		maskEndTimestamp(expected, now)
+		maskEndTimestamp(actual, now)
+	})
+}
+
+func maskEndTimestamp(traces ptrace.Traces, ts pcommon.Timestamp) {
+	for i := 0; i < traces.ResourceSpans().Len(); i++ {
+		rs := traces.ResourceSpans().At(i)
+		for j := 0; j < rs.ScopeSpans().Len(); j++ {
+			ss := rs.ScopeSpans().At(j)
+			for k := 0; k < ss.Spans().Len(); k++ {
+				span := ss.Spans().At(k)
+				span.SetEndTimestamp(ts)
+			}
+		}
+	}
+}

pkg/pdatatest/ptracetest/testdata/ignore-end-timestamp/actual.yaml

@@ -0,0 +1,22 @@
+resourceSpans:
+  - resource:
+      attributes:
+        - key: host.name
+          value:
+            stringValue: node1
+    scopeSpans:
+      - scope:
+          name: collector
+          version: v0.1.0
+        spans:
+          - attributes:
+              - key: key1
+                value:
+                  stringValue: value1
+            name: span1
+            parentSpanId: ""
+            spanId: fd0da883bb27cd6b
+            endTimeUnixNano: "11651379494838206464"
+            status: {}
+            traceId: 8c8b1765a7b0acf0b66aa4623fcb7bd5
+

pkg/pdatatest/ptracetest/testdata/ignore-end-timestamp/expected.yaml

@@ -0,0 +1,20 @@
+resourceSpans:
+  - resource:
+      attributes:
+        - key: host.name
+          value:
+            stringValue: node1
+    scopeSpans:
+      - scope:
+          name: collector
+          version: v0.1.0
+        spans:
+          - attributes:
+              - key: key1
+                value:
+                  stringValue: value1
+            name: span1
+            parentSpanId: ""
+            spanId: fd0da883bb27cd6b
+            status: {}
+            traceId: 8c8b1765a7b0acf0b66aa4623fcb7bd5

pkg/pdatatest/ptracetest/testdata/ignore-start-timestamp/actual.yaml

@@ -0,0 +1,22 @@
+resourceSpans:
+  - resource:
+      attributes:
+        - key: host.name
+          value:
+            stringValue: node1
+    scopeSpans:
+      - scope:
+          name: collector
+          version: v0.1.0
+        spans:
+          - attributes:
+              - key: key1
+                value:
+                  stringValue: value1
+            name: span1
+            parentSpanId: ""
+            spanId: fd0da883bb27cd6b
+            startTimeUnixNano: "11651379494838206464"
+            status: {}
+            traceId: 8c8b1765a7b0acf0b66aa4623fcb7bd5
+

pkg/pdatatest/ptracetest/testdata/ignore-start-timestamp/expected.yaml

@@ -0,0 +1,20 @@
+resourceSpans:
+  - resource:
+      attributes:
+        - key: host.name
+          value:
+            stringValue: node1
+    scopeSpans:
+      - scope:
+          name: collector
+          version: v0.1.0
+        spans:
+          - attributes:
+              - key: key1
+                value:
+                  stringValue: value1
+            name: span1
+            parentSpanId: ""
+            spanId: fd0da883bb27cd6b
+            status: {}
+            traceId: 8c8b1765a7b0acf0b66aa4623fcb7bd5

pkg/pdatatest/ptracetest/traces_test.go

@@ -48,6 +48,26 @@ func TestCompareTraces(t *testing.T) {
 			),
 			withOptions: nil,
 		},
+		{
+			name: "ignore-start-timestamp",
+			compareOptions: []CompareTracesOption{
+				IgnoreStartTimestamp(),
+			},
+			withoutOptions: multierr.Combine(
+				errors.New("resource \"map[host.name:node1]\": scope \"collector\": span \"span1\": start timestamp doesn't match expected: 11651379494838206464, actual: 0"),
+			),
+			withOptions: nil,
+		},
+		{
+			name: "ignore-end-timestamp",
+			compareOptions: []CompareTracesOption{
+				IgnoreEndTimestamp(),
+			},
+			withoutOptions: multierr.Combine(
+				errors.New("resource \"map[host.name:node1]\": scope \"collector\": span \"span1\": end timestamp doesn't match expected: 11651379494838206464, actual: 0"),
+			),
+			withOptions: nil,
+		},
 		{
 			name: "resourcespans-amount-unequal",
 			withoutOptions: multierr.Combine(