Generate SQL queries with comments for find operations

[chumaumenze]

Description

Closes #3573.

Readiness checklist

• I added/updated unit tests (and they pass).
• I added/updated integration/compatibility tests (and they pass).
• 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), Milestone (Next), Labels, Project and project's Sprint fields.
• I marked all done items in this checklist.

[CLAassistant]

All committers have signed the CLA.

[AlekSi]

@chumaumenze please leave a comment on #3573 so we could assign the issue

[codecov]

Codecov Report

Merging #3697 (78f08bd) into main (532787d) will decrease coverage by 0.58%.
The diff coverage is 93.33%.

Additional details and impacted files

@@            Coverage Diff             @@
##             main    #3697      +/-   ##
==========================================
- Coverage   76.75%   76.17%   -0.58%     
==========================================
  Files         323      323              
  Lines       23035    23063      +28     
==========================================
- Hits        17680    17569     -111     
- Misses       4326     4448     +122     
- Partials     1029     1046      +17     

Files	Coverage Δ
internal/backends/collection.go	100.00% <ø> (ø)
internal/backends/postgresql/collection.go	72.18% <100.00%> (+0.82%)	⬆️
internal/backends/sqlite/collection.go	80.15% <100.00%> (-0.80%)	⬇️
internal/backends/sqlite/query.go	100.00% <100.00%> (ø)
internal/backends/postgresql/query.go	92.11% <85.00%> (-1.12%)	⬇️

... and 16 files with indirect coverage changes

Flag	Coverage Δ
filter-false	?
filter-true	72.20% <82.22%> (-0.63%)	⬇️
hana-1	?
integration	72.20% <82.22%> (-0.65%)	⬇️
mongodb-1	5.46% <0.00%> (-0.01%)	⬇️
postgresql-1	52.34% <48.88%> (-0.39%)	⬇️
postgresql-2	51.65% <60.00%> (-0.27%)	⬇️
postgresql-3	50.70% <51.11%> (-0.23%)	⬇️
sort-false	72.20% <82.22%> (-0.18%)	⬇️
sort-true	?
sqlite-1	51.53% <11.11%> (-0.70%)	⬇️
sqlite-2	50.78% <22.22%> (-0.31%)	⬇️
sqlite-3	49.82% <20.00%> (-0.24%)	⬇️
unit	30.16% <93.33%> (+0.07%)	⬆️

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

[AlekSi]

@chumaumenze

FerretDB/CONTRIBUTING.md

Line 365 in 1f18df0

so there is **no need** to squash them manually, amend them, and/or do force pushes.

It makes our review process harder

[noisersup]

Thanks for the contribution! Most of the things look great, just small tweaks from me.