DuckDB dates interpreted as strings instead of timestamp

[ygg]

Check List

• Tests has been run in packages where changes 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

Issue Reference this PR resolves

Description of Changes Made (if issue reference is not provided)

CubeJS was treating DuckDB TIMESTAMPTZ data type as a string rather than a timestamp. This created problems with pre-aggregation processes, especially when trying to group data by units of time like months, weeks, etc.

[codecov]

Codecov Report

All modified and coverable lines are covered by tests ✅

Project coverage is 47.30%. Comparing base (b57ddc3) to head (04e3fcf).
Report is 2180 commits behind head on master.

Additional details and impacted files

@@            Coverage Diff             @@
##           master    #6782      +/-   ##
==========================================
- Coverage   47.32%   47.30%   -0.03%     
==========================================
  Files         155      155              
  Lines       20438    20438              
  Branches     5167     5167              
==========================================
- Hits         9673     9668       -5     
- Misses      10449    10454       +5     
  Partials      316      316              

Flag	Coverage Δ
cube-backend	47.30% <ø> (-0.03%)	⬇️

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[paveltiunov]

@ygg Thanks for contributing! Could you please add an integration or smoke test for that?

[KSDaemon]

Hi @ygg Can you elaborate when/where cube treats date_trunc's as strings rather then timestamps?