fix(logging): restore handlers and formatters on uninstrument

[sidsri14]

Description

Fixes #4949.

When LoggingInstrumentor().instrument(set_logging_format=True) is called, logging.basicConfig() configures or attaches root handlers with a format string interpolating OpenTelemetry trace context fields (%(otelTraceID)s, %(otelSpanID)s, etc.).

During _uninstrument(), the log record factory was restored to _old_factory, but the format string remained active on the root logger's handlers. Because newly created LogRecord instances no longer carried otelTraceID, any record logged after uninstrument() failed to format, causing silent log dropping and ValueError: Formatting field not found in record: 'otelTraceID' via Handler.handleError.

Changes

1. In _instrument(): When set_logging_format is active, capture the pre-instrumentation root logger state (level, handlers, and existing formatters).
2. In _uninstrument(): Restore the root logger level, restore previous formatters on pre-existing handlers, and remove any handlers added during instrumentation.
3. In tests/test_logging.py: Added unit tests verifying:
   • Logging after uninstrument() succeeds without KeyError / ValueError on formatting.
   • Pre-existing handler formatters are accurately restored after an instrument/uninstrument cycle.

Type of change

• Bug fix (non-breaking change which fixes an issue)
• New feature (non-breaking change which adds functionality)
• Breaking change (fix or feature that would cause existing functionality to not work as expected)
• This change requires a documentation update

How Has This Been Tested?

• Ran pytest instrumentation/opentelemetry-instrumentation-logging/tests: all 73 tests passed.
• Added regression tests covering both freshly configured and pre-configured logging handlers across instrument/uninstrument cycles.

Checklist:

• Followed the style guidelines of this project
• Unit tests have been added
• Documentation has been updated