fix(tracing): prevent google.protobuf import error when unloading modules [backport 1.16] (#6359)

Backport d29c860 from #6346 to 1.16.

This fix resolves an issue where the `google` module is left in a
degraded state and causes import error for `google.protobuf`.

This issue only happens when module unloading is used (gevent is
present, or manually enabled), and when stats computation is enabled.
The example scenario is present when importing `confluent-kafka`, but is
possible to happen with other integrations as well.


```
❯ DD_TRACE_COMPUTE_STATS=true ddtrace-run python -c "import confluent_kafka"
failed to import ddtrace module 'ddtrace.contrib.kafka' when patching on import
Traceback (most recent call last):
  File "/private/tmp/hoki/venv/lib/python3.10/site-packages/ddtrace/_monkey.py", line 159, in on_import
    imported_module = importlib.import_module(path)
  File "/Users/brett.langdon/.pyenv/versions/3.10.8/lib/python3.10/importlib/__init__.py", line 126, in import_module
    return _bootstrap._gcd_import(name[level:], package, level)
  File "<frozen importlib._bootstrap>", line 1050, in _gcd_import
  File "<frozen importlib._bootstrap>", line 1027, in _find_and_load
  File "<frozen importlib._bootstrap>", line 1006, in _find_and_load_unlocked
  File "<frozen importlib._bootstrap>", line 688, in _load_unlocked
  File "/private/tmp/hoki/venv/lib/python3.10/site-packages/ddtrace/internal/module.py", line 220, in _exec_module
    self.loader.exec_module(module)
  File "<frozen importlib._bootstrap_external>", line 883, in exec_module
  File "<frozen importlib._bootstrap>", line 241, in _call_with_frames_removed
  File "/private/tmp/hoki/venv/lib/python3.10/site-packages/ddtrace/contrib/kafka/__init__.py", line 51, in <module>
    from .patch import patch
  File "<frozen importlib._bootstrap>", line 1027, in _find_and_load
  File "<frozen importlib._bootstrap>", line 1006, in _find_and_load_unlocked
  File "<frozen importlib._bootstrap>", line 688, in _load_unlocked
  File "/private/tmp/hoki/venv/lib/python3.10/site-packages/ddtrace/internal/module.py", line 220, in _exec_module
    self.loader.exec_module(module)
  File "/private/tmp/hoki/venv/lib/python3.10/site-packages/ddtrace/contrib/kafka/patch.py", line 14, in <module>
    from ddtrace.internal.datastreams.processor import PROPAGATION_KEY
  File "<frozen importlib._bootstrap>", line 1027, in _find_and_load
  File "<frozen importlib._bootstrap>", line 1006, in _find_and_load_unlocked
  File "<frozen importlib._bootstrap>", line 688, in _load_unlocked
  File "/private/tmp/hoki/venv/lib/python3.10/site-packages/ddtrace/internal/module.py", line 220, in _exec_module
    self.loader.exec_module(module)
  File "/private/tmp/hoki/venv/lib/python3.10/site-packages/ddtrace/internal/datastreams/processor.py", line 17, in <module>
    from ddsketch.pb.proto import DDSketchProto
  File "<frozen importlib._bootstrap>", line 1027, in _find_and_load
  File "<frozen importlib._bootstrap>", line 1006, in _find_and_load_unlocked
  File "<frozen importlib._bootstrap>", line 688, in _load_unlocked
  File "/private/tmp/hoki/venv/lib/python3.10/site-packages/ddtrace/internal/module.py", line 220, in _exec_module
    self.loader.exec_module(module)
  File "/private/tmp/hoki/venv/lib/python3.10/site-packages/ddsketch/pb/proto.py", line 12, in <module>
    pb_version = tuple(map(int, google.protobuf.__version__.split(".")[0:2]))
AttributeError: module 'google' has no attribute 'protobuf'
```


## Testing
I was unable to create a reproduction case using subprocess tests, to
validate manually:

Via docker:
```
docker run --rm -it python:3.11 /bin/bash
# pip install ddtrace confluent-kafka
# DD_TRACE_COMPUTE_STATS=true DD_UNLOAD_MODULES_FROM_SITECUSTOMIZE=true ddtrace-run python -c "import confluent_kafka"
```

Locally:

```
virtualenv --python=3.11 venv
source venv/bin/activate

pip install ddtrace confluent-kafka
DD_TRACE_COMPUTE_STATS=true DD_UNLOAD_MODULES_FROM_SITECUSTOMIZE=true ddtrace-run python -c "import confluent_kafka"
```

## Checklist

- [x] Change(s) are motivated and described in the PR description.
- [x] Testing strategy is described if automated tests are not included
in the PR.
- [x] Risk is outlined (performance impact, potential for breakage,
maintainability, etc).
- [x] Change is maintainable (easy to change, telemetry, documentation).
- [x] [Library release note
guidelines](https://ddtrace.readthedocs.io/en/stable/releasenotes.html)
are followed. If no release note is required, add label
`changelog/no-changelog`.
- [x] Documentation is included (in-code, generated user docs, [public
corp docs](https://github.com/DataDog/documentation/)).
- [x] Backport labels are set (if
[applicable](https://ddtrace.readthedocs.io/en/latest/contributing.html#backporting))

## Reviewer Checklist

- [x] Title is accurate.
- [x] No unnecessary changes are introduced.
- [x] Description motivates each change.
- [x] Avoids breaking
[API](https://ddtrace.readthedocs.io/en/stable/versioning.html#interfaces)
changes unless absolutely necessary.
- [x] Testing strategy adequately addresses listed risk(s).
- [x] Change is maintainable (easy to change, telemetry, documentation).
- [x] Release note makes sense to a user of the library.
- [x] Reviewer has explicitly acknowledged and discussed the performance
implications of this PR as reported in the benchmarks PR comment.
- [x] 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: Brett Langdon <[email protected]>

Author: github-actions[bot]

ddtrace/bootstrap/sitecustomize.py

@@ -111,6 +111,7 @@ def drop(module_name):
             "sre_constants",  # imported by re at runtime
             "logging",
             "attr",
+            "google",
             "google.protobuf",  # the upb backend in >= 4.21 does not like being unloaded
         ]
     )

releasenotes/notes/fix-unloading-google-module-013ca2799f0964e2.yaml

@@ -0,0 +1,4 @@
+---
+fixes:
+  - |
+    tracing: This fix resolves a ``google.protobuf`` import error when module unloading.