fix(telemetry): support python3.12

[mabdinur]

Description

This PR ensures the instrumentation telemetry client is compatible with python3.12's threading module by:

• Ensuring the telemetry writer thread is only started once per application (and app-started is sent once).
• Ensuring the telemetry writer thread is disabled when an application is shutdown.
• Ensuring telemetry metrics are queued SpanAggregator.shutdown without restarting the telemetry writer thread.

Motivation

The following change failed to support the telemetry client in python3.12: #6859. This PR will hopefully fix this 🤞.

Reproduction for python3.12 runtime errors

docker run --rm -it python:3.12.0rc3 bash
root@a1f3c1d307ec:/# pip install ddtrace==2.0.0rc2
root@a1f3c1d307ec:/# python -c "import ddtrace; _ = ddtrace.tracer.trace('foo'); raise Exception"

Output

Traceback (most recent call last):
  File "<string>", line 1, in <module>
Exception
Exception ignored in atexit callback: <bound method Tracer._atexit of <ddtrace.tracer.Tracer object at 0xffffbd967260>>
Traceback (most recent call last):
  File "/usr/local/lib/python3.12/site-packages/ddtrace/tracer.py", line 293, in _atexit
    self.shutdown(timeout=self.SHUTDOWN_TIMEOUT)
  File "/usr/local/lib/python3.12/site-packages/ddtrace/tracer.py", line 1024, in shutdown
    processor.shutdown(timeout)
  File "/usr/local/lib/python3.12/site-packages/ddtrace/internal/processor/trace.py", line 270, in shutdown
    self._queue_span_count_metrics("spans_created", "integration_name", None)
  File "/usr/local/lib/python3.12/site-packages/ddtrace/internal/processor/trace.py", line 291, in _queue_span_count_metrics
    telemetry_writer.add_count_metric(
  File "/usr/local/lib/python3.12/site-packages/ddtrace/internal/telemetry/writer.py", line 514, in add_count_metric
    if self.status == ServiceStatus.RUNNING or self.enable():
                                               ^^^^^^^^^^^^^
  File "/usr/local/lib/python3.12/site-packages/ddtrace/internal/telemetry/writer.py", line 218, in enable
    self.start()
  File "/usr/local/lib/python3.12/site-packages/ddtrace/internal/service.py", line 58, in start
    self._start_service(*args, **kwargs)
  File "/usr/local/lib/python3.12/site-packages/ddtrace/internal/periodic.py", line 135, in _start_service
    self._worker.start()
  File "/usr/local/lib/python3.12/threading.py", line 971, in start
    _start_new_thread(self._bootstrap, ())
RuntimeError: can't create new thread at interpreter shutdown

Risk

This PR reverts an optimization that ensured telemetry span creation metrics were queued in batches of 100. Without this optimization we can expect a 5-10% increase to span creation and span finish.

Checklist

• Change(s) are motivated and described in the PR description.
• Testing strategy is described if automated tests are not included in the PR.
• Risk is outlined (performance impact, potential for breakage, maintainability, etc).
• Change is maintainable (easy to change, telemetry, documentation).
• Library release note guidelines are followed. If no release note is required, add label changelog/no-changelog.
• Documentation is included (in-code, generated user docs, public corp docs).
• Backport labels are set (if applicable)

Reviewer Checklist

• Title is accurate.
• No unnecessary changes are introduced.
• Description motivates each change.
• Avoids breaking API changes unless absolutely necessary.
• Testing strategy adequately addresses listed risk(s).
• Change is maintainable (easy to change, telemetry, documentation).
• Release note makes sense to a user of the library.
• Reviewer has explicitly 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
• If this PR touches code that signs or publishes builds or packages, or handles credentials of any kind, I've requested a review from @DataDog/security-design-and-guidance.
• This PR doesn't touch any of that.

[pr-commenter]

Benchmarks

Benchmark execution time: 2023-09-26 17:14:27

Comparing candidate commit 28adebd in PR branch munir/telemetry-py3.12-shutdown-exception with baseline commit 7ccb806 in branch 2.x.

Found 0 performance improvements and 0 performance regressions! Performance is the same for 90 metrics, 0 unstable metrics.