fix(ci_visibility): set up Test Optimization logging before pytest log capture [backport 3.3]

[github-actions]

Backport 2db08ec from #13030 to 3.3.

We have a recurring problem where emitting logs at the end of a pytest test session results in errors like:

Traceback (most recent call last):
  File "/usr/local/lib/python3.10/logging/__init__.py", line 1103, in emit
    stream.write(msg + self.terminator)
ValueError: I/O operation on closed file.

This happens because our plugin calls take_over_logger_stream_handler(), which calls logging.StreamHandler(), which defaults to using sys.stderr as its output stream, but by the time we call it, pytest's pytest_load_initial_conftests hook from capture.py has already executed and replaced sys.stderr with a FileIO buffer that is closed by the end of the test session, so we grab a reference to this internal FileIO buffer instead of the actual sys.stderr. This PR makes our own pytest_load_initial_conftests hook run earlier than pytest's capture.py one.

Additionally, this fixes take_over_logger_stream_handler() to copy the handler list before calling removeHandler(), as this mutates the list we are iterating through.

One user-visible side effect of this is that now we always print these logs at the beginning of the test session, regardless of whether pytest -s is used:

[Datadog CI Visibility] INFO     ddtrace.internal.ci_visibility.recorder:recorder.py:294 Service: vitor-test (env: some-env)
[Datadog CI Visibility] INFO     ddtrace.internal.ci_visibility.recorder:recorder.py:295 Requests mode: agentless
[Datadog CI Visibility] INFO     ddtrace.internal.ci_visibility.recorder:recorder.py:296 Git metadata upload enabled: True
[Datadog CI Visibility] INFO     ddtrace.internal.ci_visibility.recorder:recorder.py:297 API-provided settings: coverage collection: False
[Datadog CI Visibility] INFO     ddtrace.internal.ci_visibility.recorder:recorder.py:298 API-provided settings: Intelligent Test Runner: False, test skipping: False
[Datadog CI Visibility] INFO     ddtrace.internal.ci_visibility.recorder:recorder.py:303 API-provided settings: Early Flake Detection enabled: True
[Datadog CI Visibility] INFO     ddtrace.internal.ci_visibility.recorder:recorder.py:307 API-provided settings: Auto Test Retries enabled: True
[Datadog CI Visibility] INFO     ddtrace.internal.ci_visibility.recorder:recorder.py:308 Detected configurations: {'os.architecture': 'x86_64', 'os.platform': 'Linux', 'os.version': '6.5.0-1027-oem', 'runtime.name': 'CPython', 'runtime.version': '3.10.14'}
[Datadog CI Visibility] WARNING  ddtrace.internal.ci_visibility.recorder:recorder.py:313 CODEOWNERS file is not available
[Datadog CI Visibility] INFO     ddtrace.internal.ci_visibility.recorder:recorder.py:628 Unique tests fetched for Early Flake Detection: 34
[Datadog CI Visibility] INFO     ddtrace.internal.ci_visibility.recorder:recorder.py:576 Final settings: coverage collection: False, test skipping: False, Early Flake Detection: True, Auto Test Retries: True, Flaky Test Management: True

Whether this is a bug or a feature is up to discussion. Previously we only printed this if pytest was called with -s, more by accident than by design.

The way I managed to reproduce it was by raising an exception right after tracer shutdown in CIVisibility._stop_service():

    def _stop_service(self) -> None:
        ...
        try:
            self.tracer.shutdown()
            raise Exception("ꙮ")  # <--- added here
        except Exception:
            log.warning("Failed to shutdown tracer", exc_info=True)

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