perf: rebuild website search index in background

[ankush]

Changes:

1. Move website search index rebuilding to background
2. Don't execute all enqueued jobs synchronously during migration. This was added to accommodate the lack of Redis queue availability during the update... but that's not the case now. [patch][fix] handle enqueuing while deleting document when redis is not connected #2988

refer #17949

[codecov]

Codecov Report

Merging #17974 (9ec422e) into develop (e8af6b2) will decrease coverage by 0.02%.
The diff coverage is 70.00%.

@@             Coverage Diff             @@
##           develop   #17974      +/-   ##
===========================================
- Coverage    62.88%   62.85%   -0.03%     
===========================================
  Files          755      755              
  Lines        67911    67924      +13     
  Branches      5987     5987              
===========================================
- Hits         42705    42695      -10     
- Misses       21779    21841      +62     
+ Partials      3427     3388      -39     

Flag	Coverage Δ
server-mariadb	66.28% <66.66%> (-0.14%)	⬇️
server-ui	31.91% <33.33%> (+0.01%)	⬆️
ui-tests	50.96% <ø> (+0.09%)	⬆️

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