[Backport 2.x] Add primary first preference to all search requests

[opensearch-trigger-bot]

Backport f62f0c2 from #912.

[codecov]

Codecov Report

Merging #915 (33b4753) into 2.x (0690cdd) will increase coverage by 0.02%.
The diff coverage is 100.00%.

@@             Coverage Diff              @@
##                2.x     #915      +/-   ##
============================================
+ Coverage     75.87%   75.89%   +0.02%     
+ Complexity     2898     2896       -2     
============================================
  Files           366      366              
  Lines         16632    16637       +5     
  Branches       2413     2413              
============================================
+ Hits          12619    12627       +8     
+ Misses         2628     2626       -2     
+ Partials       1385     1384       -1     

Files Changed	Coverage Δ
...nt/indexstatemanagement/ManagedIndexCoordinator.kt	69.91% <100.00%> (+0.08%)	⬆️
...transport/action/explain/TransportExplainAction.kt	71.36% <100.00%> (+0.13%)	⬆️
...ort/action/getpolicy/TransportGetPoliciesAction.kt	86.95% <100.00%> (+0.28%)	⬆️
...t/action/indexpolicy/TransportIndexPolicyAction.kt	80.95% <100.00%> (+0.15%)	⬆️
...ent/indexstatemanagement/util/ManagedIndexUtils.kt	76.31% <100.00%> (+0.10%)	⬆️

... and 12 files with indirect coverage changes