bugfix: INSERT IGNORE not inserting rows

[systay]

Description

vtgate was failing to insert to the base table when one of the vindexes reported it had ignored a row.

Related Issue(s)

Fixes #17979

Checklist

• "Backport to:" labels have been added if this change should be back-ported to release branches
• If this change is to be back-ported to previous releases, a justification is included in the PR description
• Tests were added or are not required
• Did the new or modified tests pass consistently locally and on CI?
• Documentation was added or is not required

[vitess-bot]

Review Checklist

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[codecov]

Codecov Report

All modified and coverable lines are covered by tests ✅

Project coverage is 67.56%. Comparing base (0bf2eb1) to head (ea1c27b).
Report is 7 commits behind head on main.

Additional details and impacted files

@@            Coverage Diff             @@
##             main   #18151      +/-   ##
==========================================
+ Coverage   67.53%   67.56%   +0.02%     
==========================================
  Files        1601     1601              
  Lines      261839   261883      +44     
==========================================
+ Hits       176839   176938      +99     
+ Misses      85000    84945      -55     

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[harshit-gangal]

nit: test description