[Backport 2.x] [Refactor] more ImmutableOpenMap to jdk Map in cluster package (#7301)

[nknize]

Backport dd05edd from #7301.

[github-actions]

Gradle Check (Jenkins) Run Completed with:

• RESULT: FAILURE ❌
• URL: https://build.ci.opensearch.org/job/gradle-check/18374/
• CommitID: 5880187
  Please examine the workflow log, locate, and copy-paste the failure(s) below, then iterate to green.
  Is the failure a flaky test unrelated to your change?

[github-actions]

Gradle Check (Jenkins) Run Completed with:

• RESULT: UNSTABLE ❕
• TEST FAILURES:

      2 org.opensearch.remotestore.SegmentReplicationUsingRemoteStoreIT.testPressureServiceStats

• URL: https://build.ci.opensearch.org/job/gradle-check/18375/
• CommitID: 135ff65
  Please review all flaky tests that succeeded after retry and create an issue if one does not already exist to track the flaky failure.

[codecov]

Codecov Report

Merging #8261 (135ff65) into 2.x (77d059a) will increase coverage by 0.10%.
The diff coverage is 68.43%.

@@             Coverage Diff              @@
##                2.x    #8261      +/-   ##
============================================
+ Coverage     70.66%   70.77%   +0.10%     
- Complexity    56904    56910       +6     
============================================
  Files          4706     4706              
  Lines        269221   269180      -41     
  Branches      39796    39794       -2     
============================================
+ Hits         190250   190513     +263     
+ Misses        62657    62312     -345     
- Partials      16314    16355      +41     

Impacted Files	Coverage Δ
...apshots/status/TransportSnapshotsStatusAction.java	3.52% <0.00%> (-0.03%)	⬇️
...ing/delete/TransportDeleteDanglingIndexAction.java	9.58% <0.00%> (ø)
...rch/cluster/coordination/RemoveCustomsCommand.java	0.00% <0.00%> (ø)
...dination/UnsafeBootstrapClusterManagerCommand.java	0.00% <0.00%> (ø)
.../cluster/routing/allocation/RoutingAllocation.java	98.52% <ø> (ø)
.../src/main/java/org/opensearch/gateway/Gateway.java	8.33% <0.00%> (ø)
.../java/org/opensearch/gateway/GatewayMetaState.java	71.02% <0.00%> (-1.23%)	⬇️
...h/index/shard/RemoveCorruptedShardDataCommand.java	80.50% <ø> (-0.33%)	⬇️
...rg/opensearch/rest/action/cat/RestAliasAction.java	13.95% <0.00%> (ø)
...pensearch/rest/action/cat/RestTemplatesAction.java	22.44% <0.00%> (+0.44%)	⬆️
... and 39 more

... and 443 files with indirect coverage changes