Add more tests

[chilagrow]

Description

Closes #{issue_number}.

At the moment subcomponent operator -> is used and it uses quoted string '"64fe76829d57c1b7ded6b5de"'

sqlite> SELECT _ferretdb_sjson FROM 'chi_f5858a65' WHERE _ferretdb_sjson -> '$._id' = '"64fe76829d57c1b7ded6b5de"';
{"$s":{"p":{"_id":{"t":"objectId"},"v":{"t":"int"}},"$k":["_id","v"]},"_id":"64fe76829d57c1b7ded6b5de","v":1}

We want to replace it with subcomponent operator ->> so we can use without quoted string '64fe76829d57c1b7ded6b5de'.

sqlite> SELECT _ferretdb_sjson FROM 'chi_f5858a65' WHERE _ferretdb_sjson ->> '$._id' = '64fe76829d57c1b7ded6b5de';
{"$s":{"p":{"_id":{"t":"objectId"},"v":{"t":"int"}},"$k":["_id","v"]},"_id":"64fe76829d57c1b7ded6b5de","v":1}

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 #3336 (3c0a4db) into main (a459ba5) will increase coverage by 0.03%.
The diff coverage is 100.00%.

@@            Coverage Diff             @@
##             main    #3336      +/-   ##
==========================================
+ Coverage   73.89%   73.92%   +0.03%     
==========================================
  Files         413      413              
  Lines       25088    25096       +8     
==========================================
+ Hits        18538    18552      +14     
+ Misses       5463     5460       -3     
+ Partials     1087     1084       -3     

Files Changed	Coverage
internal/backends/sqlite/metadata/metadata.go	ø
integration/helpers.go	100.00%

Flag	Coverage Δ
hana-1	?
hana-2	?
hana-3	?
integration	70.92% <100.00%> (+0.02%)	⬆️
mongodb-1	4.76% <100.00%> (+0.05%)	⬆️
pg-1	44.93% <100.00%> (+0.61%)	⬆️
pg-2	45.08% <100.00%> (+1.22%)	⬆️
pg-3	42.66% <100.00%> (-1.10%)	⬇️
sqlite-1	43.52% <100.00%> (+0.62%)	⬆️
sqlite-2	43.30% <100.00%> (+1.30%)	⬆️
sqlite-3	41.23% <100.00%> (-1.14%)	⬇️
unit	23.27% <ø> (ø)

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

[mergify]

@chilagrow this pull request has merge conflicts.

[AlekSi]

Moved to #3340