fix: Enable tagliatelle linter rule

[majiayu000]

Fixes #2345

Changes

• Enable tagliatelle linter rule for JSON tags with snake_case convention in .golangci.yml
• Add nolint:tagliatelle directives to struct fields that use non-snake_case JSON tags for external API compatibility (PBM, Grafana, Azure, Percona version service, MongoDB)

[codecov]

Codecov Report

✅ All modified and coverable lines are covered by tests.
✅ Project coverage is 45.93%. Comparing base (4e3b1ff) to head (bfc92f7).

Additional details and impacted files

@@           Coverage Diff           @@
##               v3    #4882   +/-   ##
=======================================
  Coverage   45.93%   45.93%           
=======================================
  Files         364      364           
  Lines       37880    37880           
=======================================
  Hits        17399    17399           
- Misses      18805    18806    +1     
+ Partials     1676     1675    -1     

Flag	Coverage Δ
admin	17.82% <ø> (ø)
agent	53.53% <ø> (ø)
managed	46.57% <ø> (ø)
vmproxy	72.09% <ø> (ø)

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