Move common commands to commoncommands

[AlekSi]

Description

Refs #2650.

Readiness checklist

• I added/updated unit tests.
• I added/updated integration/compatibility tests.
• 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), Labels, Project and project's Sprint fields.
• I marked all done items in this checklist.

[codecov]

Codecov Report

Merging #2660 (9e508f5) into main (1c6136f) will increase coverage by 0.00%.
The diff coverage is 47.27%.

Additional details and impacted files

@@           Coverage Diff           @@
##             main    #2660   +/-   ##
=======================================
  Coverage   65.19%   65.19%           
=======================================
  Files         429      428    -1     
  Lines       21293    21297    +4     
=======================================
+ Hits        13881    13885    +4     
  Misses       6477     6477           
  Partials      935      935           

Impacted Files	Coverage Δ
...al/handlers/commoncommands/msg_connectionstatus.go	100.00% <ø> (ø)
internal/handlers/commoncommands/msg_currentop.go	100.00% <ø> (ø)
...rnal/handlers/commoncommands/msg_getcmdlineopts.go	0.00% <ø> (ø)
...ternal/handlers/commoncommands/msg_listcommands.go	100.00% <ø> (ø)
internal/handlers/commoncommands/msg_whatsmyuri.go	100.00% <ø> (ø)
internal/handlers/hana/msg_buildinfo.go	0.00% <0.00%> (ø)
internal/handlers/hana/msg_connectionstatus.go	0.00% <0.00%> (ø)
internal/handlers/hana/msg_currentop.go	0.00% <0.00%> (ø)
internal/handlers/hana/msg_debugerror.go	0.00% <0.00%> (ø)
internal/handlers/hana/msg_getcmdlineopts.go	0.00% <0.00%> (ø)
... and 32 more

... and 1 file with indirect coverage changes

Flag	Coverage Δ
integration	58.25% <43.63%> (+<0.01%)	⬆️
mongodb	5.21% <0.00%> (-0.01%)	⬇️
pg	58.16% <43.63%> (+<0.01%)	⬆️
unit	26.19% <25.45%> (-0.03%)	⬇️

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[chilagrow]

Thanks for this!

[w84thesun]

LGTM