Add some small improvements to the linter that checks open issues

[rumyantseva]

Description

Closes #2733.

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.

[codecov]

Codecov Report

All modified and coverable lines are covered by tests ✅

Comparison is base (235a208) 75.24% compared to head (ebfdca3) 73.81%.

Additional details and impacted files

@@            Coverage Diff             @@
##             main    #3756      +/-   ##
==========================================
- Coverage   75.24%   73.81%   -1.43%     
==========================================
  Files         330      330              
  Lines       25595    25595              
==========================================
- Hits        19258    18892     -366     
- Misses       5192     5574     +382     
+ Partials     1145     1129      -16     

see 28 files with indirect coverage changes

Flag	Coverage Δ
filter-false	?
filter-true	70.48% <ø> (-1.92%)	⬇️
hana-1	?
integration	70.48% <ø> (-1.94%)	⬇️
mongodb-1	5.08% <ø> (ø)
mysql-1	?
postgresql-1	51.00% <ø> (-14.15%)	⬇️
postgresql-2	49.62% <ø> (-0.06%)	⬇️
postgresql-3	51.91% <ø> (-0.11%)	⬇️
sqlite-1	50.18% <ø> (-14.19%)	⬇️
sqlite-2	48.63% <ø> (-0.10%)	⬇️
sqlite-3	51.17% <ø> (ø)
unit	30.82% <ø> (ø)

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

[AlekSi]

The problem with the current approach is that we process one package at a time. There is quite a lot of work we can do with more concurrency

[AlekSi]

Currently, the file that caches issues doesn't have a process to be updated.

FerretDB/Taskfile.yml

Lines 480 to 481 in f4c289f

	- bin/envtool{{exeExt}} shell rmdir tmp/checkcomments
	- bin/envtool{{exeExt}} shell mkdir tmp/checkcomments

[AlekSi]

It's not easy to make it write the message only once as run is called for each directory separately

It's a good thing we have a locked file, then…

[rumyantseva]

Thanks @henvic for your help with this PR :)