[Feature/extensions] Adding extensibility support for extension point getNamedXContents

[joshpalis]

Description

Adds support for registering named xcontent entries from extensions and transporting parse requests to extensions to generate XContent Parsers

Issues Resolved

#3379

Check List

• New functionality includes testing.
  • All tests pass
• New functionality has been documented.
  • New functionality has javadoc added
• Commits are signed per the DCO using --signoff

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[github-actions]

Gradle Check (Jenkins) Run Completed with:

• RESULT: SUCCESS ✅
• URL: https://build.ci.opensearch.org/job/gradle-check/1704/
• CommitID: 05b1ec9

[codecov-commenter]

Codecov Report

Merging #4207 (05b1ec9) into feature/extensions (ff2846a) will decrease coverage by 0.06%.
The diff coverage is 51.23%.

@@                   Coverage Diff                    @@
##             feature/extensions    #4207      +/-   ##
========================================================
- Coverage                 70.68%   70.61%   -0.07%     
+ Complexity                57173    57095      -78     
========================================================
  Files                      4612     4617       +5     
  Lines                    274812   274973     +161     
  Branches                  40227    40246      +19     
========================================================
- Hits                     194245   194183      -62     
- Misses                    64299    64451     +152     
- Partials                  16268    16339      +71     

Impacted Files	Coverage Δ
...common/xcontent/NamedXContentRegistryResponse.java	15.15% <15.15%> (ø)
...on/xcontent/NamedXContentRegistryParseRequest.java	17.39% <17.39%> (ø)
...ons/NamedXContentRegistryParseResponseHandler.java	50.00% <50.00%> (ø)
...rch/extensions/ExtensionNamedXContentRegistry.java	61.36% <61.36%> (ø)
...tensions/NamedXContentRegistryResponseHandler.java	77.08% <77.08%> (ø)
.../opensearch/extensions/ExtensionsOrchestrator.java	74.84% <100.00%> (+0.63%)	⬆️
server/src/main/java/org/opensearch/node/Node.java	86.33% <100.00%> (+0.02%)	⬆️
...a/org/opensearch/client/cluster/SniffModeInfo.java	0.00% <0.00%> (-52.95%)	⬇️
.../opensearch/client/indices/CloseIndexResponse.java	42.50% <0.00%> (-48.75%)	⬇️
...cluster/coordination/PendingClusterStateStats.java	20.00% <0.00%> (-48.00%)	⬇️
... and 458 more

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[github-actions]

Gradle Check (Jenkins) Run Completed with:

• RESULT: FAILURE ❌
• URL: https://build.ci.opensearch.org/job/gradle-check/1718/
• CommitID: 6238849

[github-actions]

Gradle Check (Jenkins) Run Completed with:

• RESULT: SUCCESS ✅
• URL: https://build.ci.opensearch.org/job/gradle-check/1729/
• CommitID: 7ca77cf