feat(api-gateway): Introduce Query format Convertion API

[KSDaemon]

This PR introduces new API endpoint /v1/convert that allows you to convert queries between different formats. Right now only sql→rest conversion is implemented, but this might be extended in the future.

• feat(api-gateway): Introduce /v1/convert API for query format conversion
• prepare backend native
• add tests

Check List

• Tests have been run in packages where changes have been made, if available
• Linter has been run for changed code
• Tests for the changes have been added if not covered yet
• Docs have been added / updated if required

[codecov]

Codecov Report

❌ Patch coverage is 8.33333% with 11 lines in your changes missing coverage. Please review.
✅ Project coverage is 77.99%. Comparing base (a8e448f) to head (78d3093).

Files with missing lines	Patch %	Lines
packages/cubejs-api-gateway/src/gateway.ts	9.09%	10 Missing ⚠️
packages/cubejs-api-gateway/src/sql-server.ts	0.00%	1 Missing ⚠️

Additional details and impacted files

@@             Coverage Diff             @@
##           master   #10286       +/-   ##
===========================================
+ Coverage   55.17%   77.99%   +22.82%     
===========================================
  Files         221      469      +248     
  Lines       17202    91662    +74460     
  Branches     3521     3523        +2     
===========================================
+ Hits         9491    71491    +62000     
- Misses       7216    19676    +12460     
  Partials      495      495               

Flag	Coverage Δ
cube-backend	55.14% <8.33%> (-0.04%)	⬇️
cubesql	83.27% <ø> (?)

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