Rename SampledFilter to TraceBasedFilter (#5862)

The specification calls this filter "TraceBased":
https://github.com/open-telemetry/opentelemetry-specification/blob/main/specification/metrics/sdk.md#tracebased

I don't have a huge preference between the two, but lean towards
TraceBasedFilter to match the specification, and to match our
environment variable configuration (and probably the future file
configuration).

This PR must be merged or closed prior to the v1.31 release, since we
can't change it after the release.

---------

Co-authored-by: Tyler Yahn <MrAlias@users.noreply.github.com>

CHANGELOG.md

@@ -10,7 +10,7 @@ This project adheres to [Semantic Versioning](https://semver.org/spec/v2.0.0.htm
 
 ### Added
 
-- Add `go.opentelemetry.io/otel/sdk/metric/exemplar` package which includes `Exemplar`, `Filter`, `SampledFilter`, `AlwaysOnFilter`, `HistogramReservoir`, `FixedSizeReservoir`, `Reservoir`, `Value` and `ValueType` types. These will be used for configuring the exemplar reservoir for the metrics sdk. (#5747)
+- Add `go.opentelemetry.io/otel/sdk/metric/exemplar` package which includes `Exemplar`, `Filter`, `TraceBasedFilter`, `AlwaysOnFilter`, `HistogramReservoir`, `FixedSizeReservoir`, `Reservoir`, `Value` and `ValueType` types. These will be used for configuring the exemplar reservoir for the metrics sdk. (#5747, #5862)
 
 ### Changed
 

sdk/metric/exemplar.go

@@ -33,7 +33,7 @@ func reservoirFunc[N int64 | float64](agg Aggregation) func() aggregate.Filtered
 	case "trace_based":
 		fallthrough
 	default:
-		filter = exemplar.SampledFilter
+		filter = exemplar.TraceBasedFilter
 	}
 
 	// https://github.com/open-telemetry/opentelemetry-specification/blob/d4b241f451674e8f611bb589477680341006ad2b/specification/metrics/sdk.md#exemplar-defaults

sdk/metric/exemplar/filter.go

@@ -16,10 +16,10 @@ import (
 // Reservoir in making a sampling decision.
 type Filter func(context.Context) bool
 
-// SampledFilter is a [Filter] that will only offer measurements
+// TraceBasedFilter is a [Filter] that will only offer measurements
 // if the passed context associated with the measurement contains a sampled
 // [go.opentelemetry.io/otel/trace.SpanContext].
-func SampledFilter(ctx context.Context) bool {
+func TraceBasedFilter(ctx context.Context) bool {
 	return trace.SpanContextFromContext(ctx).IsSampled()
 }
 

sdk/metric/exemplar/filter_test.go

@@ -12,16 +12,16 @@ import (
 	"go.opentelemetry.io/otel/trace"
 )
 
-func TestSampledFilter(t *testing.T) {
-	t.Run("Int64", testSampledFiltered[int64])
-	t.Run("Float64", testSampledFiltered[float64])
+func TestTraceBasedFilter(t *testing.T) {
+	t.Run("Int64", testTraceBasedFilter[int64])
+	t.Run("Float64", testTraceBasedFilter[float64])
 }
 
-func testSampledFiltered[N int64 | float64](t *testing.T) {
+func testTraceBasedFilter[N int64 | float64](t *testing.T) {
 	ctx := context.Background()
 
-	assert.False(t, SampledFilter(ctx), "non-sampled context should not be offered")
-	assert.True(t, SampledFilter(sample(ctx)), "sampled context should be offered")
+	assert.False(t, TraceBasedFilter(ctx), "non-sampled context should not be offered")
+	assert.True(t, TraceBasedFilter(sample(ctx)), "sampled context should be offered")
 }
 
 func sample(parent context.Context) context.Context {