YDB: support pushdown for optional types in Query Service mode

[vitalyisaev2]

No description provided.

[codecov]

Codecov Report

Attention: Patch coverage is 89.47368% with 2 lines in your changes missing coverage. Please review.

Project coverage is 65.02%. Comparing base (f76af43) to head (5579a74).
Report is 1 commits behind head on main.

Files with missing lines	Patch %	Lines
...p/server/datasource/rdbms/ydb/connection_native.go	88.23%	2 Missing ⚠️

Additional details and impacted files

@@            Coverage Diff             @@
##             main     #204      +/-   ##
==========================================
+ Coverage   63.40%   65.02%   +1.62%     
==========================================
  Files         107      107              
  Lines        5998     6010      +12     
==========================================
+ Hits         3803     3908     +105     
+ Misses       1881     1776     -105     
- Partials      314      326      +12     

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