fix: correct index syncing

[ankush]

The implementation of syncing unique and non-unique index depended on
index names which used to be different before because of that there's
tendency to incorrectly identify index.

This PR adds a separate util for checking if a column has index without
relying on naming convention. It just goes and checks if there's any
index with that column in it, hence far more reliable.

Caused by #15680

PS: This also fixes issue where columns having search + unique index were not dropped automatically.

[codecov]

Codecov Report

Merging #18262 (1d8f58c) into develop (d597acb) will decrease coverage by 0.16%.
The diff coverage is 64.70%.

❗ Current head 1d8f58c differs from pull request most recent head da561c2. Consider uploading reports for the commit da561c2 to get more accurate results

Additional details and impacted files

@@             Coverage Diff             @@
##           develop   #18262      +/-   ##
===========================================
- Coverage    62.68%   62.51%   -0.17%     
===========================================
  Files          746      744       -2     
  Lines        67327    67717     +390     
  Branches      5965     5962       -3     
===========================================
+ Hits         42206    42336     +130     
- Misses       21630    21852     +222     
- Partials      3491     3529      +38     

Flag	Coverage Δ
server-mariadb	66.86% <94.73%> (+0.02%)	⬆️

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