fix(tracer): add extra service names for all spans [backport 3.10] (#13943)

Backport ab14f5c from #13922 to 3.10.

Add extra service names for all finished spans.

From a suggestion of @brettlangdon 

APPSEC-58108

## Checklist
- [x] PR author has checked that all the criteria below are met
- The PR description includes an overview of the change
- The PR description articulates the motivation for the change
- The change includes tests OR the PR description describes a testing
strategy
- The PR description notes risks associated with the change, if any
- Newly-added code is easy to change
- The change follows the [library release note
guidelines](https://ddtrace.readthedocs.io/en/stable/releasenotes.html)
- The change includes or references documentation updates if necessary
- Backport labels are set (if
[applicable](https://ddtrace.readthedocs.io/en/latest/contributing.html#backporting))

## Reviewer Checklist
- [x] Reviewer has checked that all the criteria below are met 
- Title is accurate
- All changes are related to the pull request's stated goal
- Avoids breaking
[API](https://ddtrace.readthedocs.io/en/stable/versioning.html#interfaces)
changes
- Testing strategy adequately addresses listed risks
- Newly-added code is easy to change
- Release note makes sense to a user of the library
- If necessary, author has acknowledged and discussed the performance
implications of this PR as reported in the benchmarks PR comment
- Backport labels are set in a manner that is consistent with the
[release branch maintenance
policy](https://ddtrace.readthedocs.io/en/latest/contributing.html#backporting)

Co-authored-by: brettlangdon <brett.langdon@datadoghq.com>

Author: github-actions[bot]

ddtrace/_trace/processor/__init__.py

@@ -394,6 +394,11 @@ def on_span_finish(self, span: Span) -> None:
                         log.error("error applying processor %r", tp, exc_info=True)
 
                 self._queue_span_count_metrics("spans_finished", "integration_name")
+                if spans is not None:
+                    for span in spans:
+                        if span.service:
+                            # report extra service name as it may have been set after the span creation by the customer
+                            config._add_extra_service(span.service)
                 self.writer.write(spans)
                 return
 

releasenotes/notes/report_extra_service_names_from_spans-b98b87fbefe97337.yaml

@@ -0,0 +1,4 @@
+---
+fixes:
+  - |
+    Tracer: This fix resolves an issue where programmatically set span services names would not get reported to Remote Configuration.

tests/internal/service_name/test_extra_services_names.py

@@ -85,3 +85,28 @@ def test_config_extra_service_names_rc_disabled(run_python_code_in_subprocess):
     env["DD_REMOTE_CONFIGURATION_ENABLED"] = "false"
     stdout, stderr, status, _ = run_python_code_in_subprocess(code, env=env)
     assert status == 0, (stdout, stderr, status)
+
+
+def test_config_extra_service_names_customer_changes(run_python_code_in_subprocess):
+    code = """
+import ddtrace.auto
+import ddtrace
+import re
+import os
+import sys
+import time
+
+with ddtrace.tracer.trace("test") as parent:
+    parent.service = "parent_service"
+    with ddtrace.tracer.trace("child") as child:
+        child.service = "child_service"
+extra_services = ddtrace.config._get_extra_services()
+# collecting extra services in all spans, including the parent and child
+assert "parent_service" in extra_services
+assert "child_service" in extra_services
+    """
+
+    env = os.environ.copy()
+    env["DD_REMOTE_CONFIGURATION_ENABLED"] = "true"
+    stdout, stderr, status, _ = run_python_code_in_subprocess(code, env=env)
+    assert status == 0, (stdout, stderr, status)