Fix ACL checks for CTEs (#16642)

[systay]

This PR is a backport of #16642 to latest-20.0

This PR is the cherry-pick of #16642

Description

This PR fixes the issue described in #16542 and supersedes #16548.

The ACLs for a CTE were failing because a new table is being defined and it doesn't require any permission checks. This PR fixes the issue by keeping track of the CTE scopes seen while building permissions. We use this to know if the table that we're trying to check permissions for is a CTE or not. If it is, then we conclude that the table doesn't require a permission check.

[vitess-bot]

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[codecov]

Codecov Report

All modified and coverable lines are covered by tests ✅

Project coverage is 68.67%. Comparing base (4a0aab6) to head (28fd66e).

Additional details and impacted files

@@               Coverage Diff                @@
##           release-20.0   #16775      +/-   ##
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- Coverage         68.68%   68.67%   -0.01%     
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  Files              1541     1541              
  Lines            197937   197937              
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- Hits             135945   135933      -12     
- Misses            61992    62004      +12     

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