[release-22.0] Fix cross shard/keyspace joins with derived tables containing a UNION. (#19046)

[vitess-bot]

Description

This is a backport of #19046

[vitess-bot]

Hello @arthurschreiber, there are conflicts in this backport.

Please address them in order to merge this Pull Request. You can execute the snippet below to reset your branch and resolve the conflict manually.

Make sure you replace origin by the name of the vitessio/vitess remote

git fetch --all
gh pr checkout 19136
git reset --hard origin/release-22.0
git cherry-pick -m 1 737e635fbde13a302c4a0e3dc50319c634ddefd0

[codecov]

Codecov Report

✅ All modified and coverable lines are covered by tests.
✅ Project coverage is 69.73%. Comparing base (c510d1d) to head (6301e8b).
⚠️ Report is 1 commits behind head on release-22.0.

Additional details and impacted files

@@              Coverage Diff              @@
##           release-22.0   #19136   +/-   ##
=============================================
  Coverage         69.73%   69.73%           
=============================================
  Files              1601     1601           
  Lines            213316   213319    +3     
=============================================
+ Hits             148757   148764    +7     
+ Misses            64559    64555    -4     

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