feat(traceloop-sdk): harden LoggerWrapper + add SpanPostprocessCallbackProcessor

[sayonfortify]

• I have added tests that cover my changes.
• If adding a new instrumentation or changing an existing one, I've added screenshots from some observability platform showing the change. (N/A — not a new instrumentation)
• PR name follows conventional commits format: feat(instrumentation): ... or fix(instrumentation): ....
• (If applicable) I have updated the documentation accordingly.

Changes

traceloop/sdk/logging/logging.py

• Replace destructive logging.basicConfig() with non-destructive _attach_root_logging_handler() — preserves existing app logging handlers/levels
• Add LoggingInstrumentor idempotency guard (is_instrumented_by_opentelemetry)
• Add get_logging_provider() class method on LoggerWrapper
• Add is_fortifyroot_logging_handler() helper for marker-based handler cleanup

traceloop/sdk/tracing/tracing.py

• Replace monkey-patching on_end with proper _SpanPostprocessCallbackProcessor (implements SpanProcessor)
• Wire callback processor via add_span_processor() in all 3 init paths (list, single, default)

Why

These changes enable reliable span-end hooks for synthetic log emission in the FortifyRoot SDK, without breaking existing app logging configurations.

Testing

Tests are in fortifyroot-sdk-py (consumer repo) — validated with 262 passing tests + live Postman API verification.