fix(er): prioritize tb from exception object (#14465)

We retrieve the traceback object from the exception object itself, if
available and prioritize it over the traceback component of the
exception info tuple. Some frameworks, such as Celery, might modify the
exception info tuple by passing around a custom traceback object that
might not have all the information required by Exception Replay.

## Testing Strategy

We tested that we can retrieve local variables in ER when Celery tasks
throw exceptions with this change.

## Checklist
- [ ] PR author has checked that all the criteria below are met
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- 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
- [ ] 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
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implications of this PR as reported in the benchmarks PR comment
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[release branch maintenance
policy](https://ddtrace.readthedocs.io/en/latest/contributing.html#backporting)

Author: P403n1x87

ddtrace/debugging/_exception/replay.py

@@ -266,12 +266,16 @@ def _capture_tb_frame_for_span(
         return snapshot is not None
 
     def on_span_exception(
-        self, span: Span, _exc_type: t.Type[BaseException], exc: BaseException, tb: t.Optional[TracebackType]
+        self, span: Span, _exc_type: t.Type[BaseException], exc: BaseException, traceback: t.Optional[TracebackType]
     ) -> None:
         if span.get_tag(DEBUG_INFO_TAG) == "true" or not can_capture(span):
             # Debug info for span already captured or no budget to capture
             return
 
+        # Prioritize the traceback from the exception, if available. Some
+        # frameworks (like celery) may modify the traceback object that is
+        # passed to the exception handler.
+        tb = exc.__traceback__ or traceback
         chain, exc_id = unwind_exception_chain(exc, tb)
         if not chain or exc_id is None:
             # No exceptions to capture

releasenotes/notes/fix-er-tb-priority-77dc656bdb2c4802.yaml

@@ -0,0 +1,5 @@
+---
+fixes:
+  - |
+    exception replay: fixed an issue that prevented snapshots from retrieving
+    local variables from traceback frames from exception thrown by Celery tasks.