schemadiff: fix index/foreign-key apply scenario

[shlomi-noach]

Description

Fixes #16697 by doing two iteration over the ALTER TABLE options in apply(). Most validations take place on the first iteration. The (newly introduced) second iteration is now able to validate changes after applying all the options.

Related Issue(s)

#16697

Checklist

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Deployment Notes

[vitess-bot]

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[codecov]

Codecov Report

Attention: Patch coverage is 94.82759% with 3 lines in your changes missing coverage. Please review.

Project coverage is 68.95%. Comparing base (44e96c2) to head (ec350db).
Report is 4 commits behind head on main.

Files with missing lines	Patch %	Lines
go/vt/schemadiff/table.go	94.82%	3 Missing ⚠️

Additional details and impacted files

@@           Coverage Diff           @@
##             main   #16698   +/-   ##
=======================================
  Coverage   68.94%   68.95%           
=======================================
  Files        1565     1565           
  Lines      201653   201699   +46     
=======================================
+ Hits       139033   139075   +42     
- Misses      62620    62624    +4     

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[shlomi-noach]

Further changes in this PR: schemadiff now detects scenarios where an index is renamed, ie. an index is dropped, and a new index is added in its place with the exact same definition other than the name. In such cases, schemadiff replaces the ADD+DROP clauses with one RENAME INDEX clause.

[dbussink]

Fix for the CI errors here is in #16702