Setup OpenTelemetry exporter for FerretDB

[rumyantseva]

Description

Closes #4345.

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

Attention: Patch coverage is 65.78947% with 13 lines in your changes missing coverage. Please review.

Project coverage is 73.90%. Comparing base (bcb3ee1) to head (873dba7).

Additional details and impacted files

@@            Coverage Diff             @@
##             main    #4380      +/-   ##
==========================================
- Coverage   74.19%   73.90%   -0.29%     
==========================================
  Files         323      323              
  Lines       22419    22447      +28     
==========================================
- Hits        16634    16590      -44     
- Misses       4568     4635      +67     
- Partials     1217     1222       +5     

Files	Coverage Δ
integration/setup/startup.go	63.88% <83.33%> (+6.07%)	⬆️
internal/util/observability/observability.go	68.57% <57.69%> (-31.43%)	⬇️

... and 9 files with indirect coverage changes

Flag	Coverage Δ
filter-true	67.37% <65.78%> (-0.33%)	⬇️
hana-1	?
integration	67.37% <65.78%> (-0.33%)	⬇️
mongodb-1	5.20% <65.78%> (+0.07%)	⬆️
postgresql-1	43.94% <65.78%> (+0.02%)	⬆️
postgresql-2	44.98% <65.78%> (+0.06%)	⬆️
postgresql-3	43.02% <65.78%> (+0.04%)	⬆️
postgresql-4	40.31% <65.78%> (+0.03%)	⬆️
postgresql-5	43.80% <65.78%> (+0.10%)	⬆️
sqlite-1	43.17% <65.78%> (+0.01%)	⬆️
sqlite-2	44.02% <65.78%> (-0.05%)	⬇️
sqlite-3	42.25% <65.78%> (+0.02%)	⬆️
sqlite-4	39.46% <65.78%> (+0.03%)	⬆️
sqlite-5	43.04% <65.78%> (+0.02%)	⬆️
unit	32.88% <0.00%> (-0.11%)	⬇️

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

[AlekSi]

It should be configurable with --test-XXX flags.

They should be under the Test group

[mergify]

@rumyantseva this pull request has merge conflicts.