Fix thread name CallsiteParameterAdder in async methods (issue #710)

[BlocksecPHD]

Problem

When using async logging methods (.ainfo(), etc.), the CallsiteParameterAdder processor was collecting thread information from the executor thread pool instead of the caller's thread. This caused thread_name to show 'asyncio_0' instead of the actual caller thread like 'MainThread'.

Solution

This fix captures thread info (thread_id and thread_name) before passing control to the executor thread, storing it in a contextvar (_ASYNC_CALLING_THREAD) that is copied along with the calling stack frame. The processor then uses this captured thread info when available.

Changes

1. contextvars.py: Added _ASYNC_CALLING_THREAD contextvar to store captured thread info
2. _native.py: Updated async methods to capture thread info before executor
3. stdlib.py: Updated async methods in both BoundLogger and AsyncBoundLogger to capture thread info
4. processors.py: Updated _get_callsite_thread and _get_callsite_thread_name to use captured info from contextvar
5. tests: Added tests to verify thread info is correctly captured in async context

Testing

All tests pass:

• Native async tests
• Stdlib async tests
• AsyncBoundLogger tests
• Existing processor tests

Example Output

Before fix:

thread_name=asyncio_0  # Wrong - executor thread

After fix:

thread_name=MainThread  # Correct - caller's thread

Fixes #710