Add a test script to show that $pullAll does not remove all specified elements

[AlekSi]

Moved from #2108.

Description

Closes #2109

This PR adds a script to show that $pullAll does not remove all instances from the array.

Readiness checklist

• I added/updated unit tests.
• I added/updated integration/compatibility tests.
• I added/updated comments and checked rendering.
• I made spot refactorings.
• I updated user documentation.
• I ran task all, and it passed.
• I ensured that PR title is good enough for the changelog.
• (for maintainers only) I set Reviewers (@FerretDB/core), Assignee, Labels, Project and project's Sprint fields.
• I marked all done items in this checklist.

[codecov]

Codecov Report

All modified and coverable lines are covered by tests ✅

Project coverage is 72.14%. Comparing base (5656ccc) to head (6294eab).
Report is 159 commits behind head on main.

Additional details and impacted files

@@            Coverage Diff             @@
##             main    #4322      +/-   ##
==========================================
- Coverage   75.33%   72.14%   -3.19%     
==========================================
  Files         326      326              
  Lines       22414    22414              
==========================================
- Hits        16885    16170     -715     
- Misses       4306     5010     +704     
- Partials     1223     1234      +11     

see 47 files with indirect coverage changes

Flag	Coverage Δ
filter-false	?
filter-true	65.22% <ø> (-3.76%)	⬇️
hana-1	?
integration	65.22% <ø> (-3.80%)	⬇️
mongodb-1	5.14% <ø> (+<0.01%)	⬆️
mysql-1	?
mysql-2	?
mysql-3	?
postgresql-1	44.70% <ø> (-8.53%)	⬇️
postgresql-2	44.85% <ø> (-9.63%)	⬇️
postgresql-3	41.54% <ø> (-12.04%)	⬇️
postgresql-4	?
postgresql-5	43.36% <ø> (-0.01%)	⬇️
sqlite-1	43.81% <ø> (-8.39%)	⬇️
sqlite-2	44.20% <ø> (-9.28%)	⬇️
sqlite-3	40.78% <ø> (-11.99%)	⬇️
sqlite-4	?
sqlite-5	42.49% <ø> (ø)
unit	33.22% <ø> (ø)

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[AlekSi]

Test passes now