Fix memory leak on objects passed to init, update, or extend

[bdraco]

fixes #1117

[codspeed-hq]

CodSpeed Performance Report

Merging #1121 will not alter performance

_{Comparing fix_leak (9270505) with master (9a32040)}

Summary

✅ 244 untouched benchmarks

[codecov]

Codecov Report

Attention: Patch coverage is 72.72727% with 6 lines in your changes missing coverage. Please review.

Project coverage is 91.30%. Comparing base (9a32040) to head (9270505).
Report is 1 commits behind head on master.

Files with missing lines	Patch %	Lines
tests/test_multidict.py	72.72%	6 Missing ⚠️

❌ Your project status has failed because the head coverage (83.71%) is below the target coverage (85.00%). You can increase the head coverage or adjust the target coverage.

Additional details and impacted files

@@            Coverage Diff             @@
##           master    #1121      +/-   ##
==========================================
- Coverage   91.36%   91.30%   -0.07%     
==========================================
  Files          52       52              
  Lines        6349     6391      +42     
  Branches      627      627              
==========================================
+ Hits         5801     5835      +34     
- Misses        113      121       +8     
  Partials      435      435              

Flag	Coverage Δ
CI-GHA	91.30% <72.72%> (-0.07%)	⬇️
MyPy	83.71% <72.72%> (-0.08%)	⬇️
pytest	99.89% <ø> (-0.07%)	⬇️

Flags with carried forward coverage won't be shown. Click here to find out more.

☔ View full report in Codecov by Sentry.
📢 Have feedback on the report? Share it here.

🚀 New features to boost your workflow:

• ❄️ Test Analytics: Detect flaky tests, report on failures, and find test suite problems.

[asvetlov]

Good finding.
Let's apply a little different fix.
_multidict_extend_parse_args() should incref all returned values; I suggest you don't change it.
But the caller should decref.
This is the standard practice in Python, let's keep it.

[asvetlov]

Please take a look at the current PR's state.
It fixes the bug but avoids reference stealing.
Borrowed references are dangerous, in CPython itself we are trying to get rid of them everywhere

[bdraco]

Thanks! Thats much better and safer. 🚀

Will clean it up, add changelog, and get it shipped

[bdraco]

If you get a chance, aio-libs/yarl#1456 could use a followup review.