Fix __tracebackhide__ for ExceptionGroup frames sharing a source location

[Amine-LG]

Fixes #14940.

_filter_tracebackexception() matched filtered traceback entries to Python's formatted frames using (filename, line number). Separate traceback entries can share those values while having different __tracebackhide__ values, causing a hidden frame to remain visible.

This change identifies each occurrence by the identity of its underlying raw traceback entry instead. Pytest's TracebackEntry and Python's FrameSummary sequences preserve traceback order, so they are walked together and only occurrences that survived filtering are kept.

The pairing is non-strict because sys.tracebacklimit can shorten Python's formatted traceback. A separate test protects that behavior.

This is a follow-up to the ExceptionGroup traceback filtering added in #14649.

Tests

• Added a regression test for visible and hidden recursive calls from the same line.
• Added a regression test for a shortened traceback when sys.tracebacklimit is set.
• python -m pytest -q testing/code
• pre-commit run --files AUTHORS changelog/14940.bugfix.rst src/_pytest/_code/code.py testing/code/test_excinfo.py

AI assistance

I used AI tools during the investigation and implementation. I manually reproduced the issue and reviewed and tested the final changes.