Implement createIndexes for SQLite

[rumyantseva]

Description

Closes #3176.

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

Merging #3304 (6f5dbac) into main (4af1da0) will increase coverage by 0.12%.
The diff coverage is 80.19%.

@@            Coverage Diff             @@
##             main    #3304      +/-   ##
==========================================
+ Coverage   73.75%   73.88%   +0.12%     
==========================================
  Files         412      413       +1     
  Lines       24583    25034     +451     
==========================================
+ Hits        18131    18496     +365     
- Misses       5379     5456      +77     
- Partials     1073     1082       +9     

Files Changed	Coverage
internal/backends/decorators/dummy/collection.go	0.00%
internal/backends/decorators/oplog/collection.go	0.00%
internal/backends/postgresql/collection.go	0.00%
internal/backends/sqlite/metadata/metadata.go	56.81%
internal/backends/sqlite/metadata/registry.go	76.33%
internal/handlers/sqlite/msg_createindexes.go	83.89%
internal/backends/collection.go	100.00%
internal/backends/sqlite/collection.go	100.00%
internal/backends/sqlite/metadata/pool/pool.go	100.00%

Flag	Coverage Δ
hana-1	?
hana-2	?
hana-3	?
integration	70.87% <80.49%> (+0.20%)	⬆️
mongodb-1	4.72% <0.00%> (-0.09%)	⬇️
pg-1	44.40% <0.00%> (-0.83%)	⬇️
pg-2	43.94% <0.00%> (-0.82%)	⬇️
pg-3	43.90% <0.00%> (-0.92%)	⬇️
sqlite-1	42.78% <72.65%> (+0.55%)	⬆️
sqlite-2	41.93% <56.40%> (+0.22%)	⬆️
sqlite-3	42.14% <54.49%> (+0.12%)	⬆️
unit	23.29% <17.71%> (-0.18%)	⬇️

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[rumyantseva]

Ok, the problem with unit tests is because of TestCreateSameStress doesn't work. I don't see what exactly happens, the way how mutex is used looks correct to me, so I'm still investigating the problems. Suggestions are welcome.