Use bson2 package for wire queries and replies

[AlekSi]

Description

That would allow us to avoid extra copying in the future.

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: 69 lines in your changes are missing coverage. Please review.

Comparison is base (9de2931) 76.17% compared to head (6209c8b) 75.11%.

Additional details and impacted files

@@            Coverage Diff             @@
##             main    #4108      +/-   ##
==========================================
- Coverage   76.17%   75.11%   -1.06%     
==========================================
  Files         349      349              
  Lines       22157    22162       +5     
==========================================
- Hits        16877    16647     -230     
- Misses       3966     4251     +285     
+ Partials     1314     1264      -50     

Files	Coverage Δ
internal/handler/common/ismaster.go	73.07% <100.00%> (-1.00%)	⬇️
internal/wire/op_msg.go	60.32% <100.00%> (-0.85%)	⬇️
internal/handler/cmd_query.go	25.00% <0.00%> (+1.19%)	⬆️
internal/wire/msg_body.go	47.56% <33.33%> (ø)
internal/wire/op_reply.go	50.00% <46.15%> (+5.55%)	⬆️
internal/wire/op_query.go	46.91% <42.42%> (+10.68%)	⬆️

... and 16 files with indirect coverage changes

Flag	Coverage Δ
filter-true	67.41% <31.74%> (-0.37%)	⬇️
hana-1	?
integration	67.41% <31.74%> (-0.37%)	⬇️
mongodb-1	4.73% <0.00%> (-0.01%)	⬇️
postgresql-1	49.14% <31.74%> (+0.93%)	⬆️
postgresql-2	48.71% <30.95%> (+0.98%)	⬆️
postgresql-3	48.79% <31.74%> (+0.88%)	⬆️
sqlite-1	48.24% <31.74%> (+0.86%)	⬆️
sqlite-2	47.91% <30.95%> (+0.88%)	⬆️
sqlite-3	47.96% <31.74%> (+0.89%)	⬆️
unit	33.14% <42.06%> (+0.06%)	⬆️

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

[rumyantseva]

Looks good!

[chilagrow]

I like the new way of using indexes to marshal/unmarshal query and reply.