gh-150072: Optimize logging imports by lazily importing traceback

[ByteFlowing1337]

• Issue: Lazily import traceback in logging #150072

[hugovk]

Unfortunately the lazy import fails when trying to test logging during shutdown:

======================================================================
FAIL: test_logging_at_shutdown (test.test_logging.ModuleLevelMiscTest.test_logging_at_shutdown)
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Traceback (most recent call last):
  File "/Users/runner/work/cpython/cpython/Lib/test/test_logging.py", line 5259, in test_logging_at_shutdown
    self.assertIn("exception in __del__", err)
    ~~~~~~~~~~~~~^^^^^^^^^^^^^^^^^^^^^^^^^^^^^
AssertionError: 'exception in __del__' not found in '--- Logging error ---\nException ignored while calling deallocator <function A.__del__ at 0x20002d3e8d0>:\nTraceback (most recent call last):\n  File "<string>", line 9, in __del__\n  File "/Users/runner/work/cpython/cpython/Lib/logging/__init__.py", line 2194, in exception\n  File "/Users/runner/work/cpython/cpython/Lib/logging/__init__.py", line 2186, in error\n  File "/Users/runner/work/cpython/cpython/Lib/logging/__init__.py", line 1553, in error\n  File "/Users/runner/work/cpython/cpython/Lib/logging/__init__.py", line 1669, in _log\n  File "/Users/runner/work/cpython/cpython/Lib/logging/__init__.py", line 1685, in handle\n  File "/Users/runner/work/cpython/cpython/Lib/logging/__init__.py", line 1741, in callHandlers\n  File "/Users/runner/work/cpython/cpython/Lib/logging/__init__.py", line 1031, in handle\n  File "/Users/runner/work/cpython/cpython/Lib/logging/__init__.py", line 1163, in emit\n  File "/Users/runner/work/cpython/cpython/Lib/logging/__init__.py", line 1080, in handleError\nImportError: sys.meta_path is None, Python is likely shutting down\n'

[ByteFlowing1337]

We can fix the test by adding atexit.register(lambda: traceback) in __init__.py, which guarantees traceback will be imported before the interpreter cleans up. But sadly, the wall-clock time will still be unoptimized in that case.

[picnixz]

I would prefer that we do not overcomplicate atexit callbacks in this case.