Fix enum value collision between AllocatorType and ObjectTrackingEvent

[pablogsal]

The ObjectTrackingEvent enum values were colliding with AllocatorType
values. This caused a bug where OBJECT_DESTROYED (value 2) was
incorrectly matching PYOBJECT_MALLOC in the deallocation check.

This would incorrectly treat pymalloc allocations as deallocations when
checking stack traces. The bug went undetected because we lacked tests
for Python allocations with trace_python_allocators enabled.

Fixed by changing ObjectTrackingEvent values to 10 and 20 to avoid
collision. Added test coverage for pymalloc allocations with Python
stack traces to prevent regressions.

Issue number of the reported bug or feature request: #

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Testing performed
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Additional context
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[codecov-commenter]

Codecov Report

❌ Patch coverage is 96.29630% with 1 line in your changes missing coverage. Please review.
✅ Project coverage is 92.35%. Comparing base (6cfb8a4) to head (dc85b8c).

Files with missing lines	Patch %	Lines
tests/integration/test_tracking.py	96.15%	1 Missing ⚠️

Additional details and impacted files

@@            Coverage Diff             @@
##             main     #832      +/-   ##
==========================================
- Coverage   92.43%   92.35%   -0.08%     
==========================================
  Files          99       99              
  Lines       11814    11840      +26     
  Branches      423      425       +2     
==========================================
+ Hits        10920    10935      +15     
- Misses        894      905      +11     

Flag	Coverage Δ
cpp	92.35% <96.29%> (-0.08%)	⬇️
python_and_cython	92.35% <96.29%> (-0.08%)	⬇️

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[godlygeek]

I pushed three tiny changes:

• a fix to the grammar in the news entry
• a change to the enumerators' values to ensure they don't conflict (the 10 you chose still conflicted; ALIGNED_ALLOC == 10 == OBJECT_CREATED!) - I just picked a different convention; one enum's enumerators count up from 1 and the other's count down from negative 1, and we'll never get conflicts.
• I added a comment explaining that they need to not conflict.