gh-132372

This speeds up logging.config.fileConfig() and logging.config.dictConfig() when they need to handle many existing loggers while disable_existing_loggers is active.

The old code kept the existing logger names in a sorted list, but still used repeated list membership, index(), tail scans, and remove() calls for every configured logger. This keeps the sorted list for child logger ordering, uses a set for membership/removal tracking, and uses bisect_left() to jump directly to the dotted child logger range.

Validation:

• PCbuild\amd64\python_d.exe -m test test_logging -j0
• PCbuild\amd64\python_d.exe Tools\patchcheck\patchcheck.py
• git diff --check

Benchmark:

Loaded origin/main:Lib/logging/config.py and the patched Lib/logging/config.py into the same Python 3.12.8 release interpreter, then timed only the dictConfig() call while resetting identical existing logger state outside the timer.

dictConfig-existing-loggers-old-100: Mean +- std dev: 5.68 ms +- 0.18 ms
dictConfig-existing-loggers-new-100: Mean +- std dev: 3.92 ms +- 0.11 ms
speedup: 1.45x

dictConfig-existing-loggers-old-500: Mean +- std dev: 130 ms +- 3 ms
dictConfig-existing-loggers-new-500: Mean +- std dev: 82.6 ms +- 2.6 ms
speedup: 1.57x