[Extensions] Handle Deprecated and Replaced Routes in Extension Rest Handlers

[dbwiddis]

Companion PR on SDK: opensearch-project/opensearch-sdk-java#666

Description

Adds the ability to handle Deprecated and Replaced Routes to the ExtensionRestHandler. This will permit (nearly) identical syntax for plugin migration, and provide backwards compatibility to extension users.

• Routes were already registered.
• Deprecated routes are just a wrapper around Routes, which add a log message.
• Replaced routes are a fancy user interface to simultaneously register Routes and Deprecated Routes.

The OpenSearch integration adds a new list to the existing registration request. In addition to the method and path sent for routes, deprecated routes have a deprecationMessage included. This is included in a separate list where the message immediately follows the method/path.

Issues Resolved

Fixes SDK #665

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
  Commit changes are listed out in CHANGELOG.md file (See: Changelog)

By submitting this pull request, I confirm that my contribution is made under the terms of the Apache 2.0 license.
For more information on following Developer Certificate of Origin and signing off your commits, please check here.

[github-actions]

Gradle Check (Jenkins) Run Completed with:

• RESULT: UNSTABLE ❕
• TEST FAILURES:

      1 org.opensearch.indices.replication.SegmentReplicationIT.testScrollWithOngoingSegmentReplication
      1 org.opensearch.cluster.routing.allocation.decider.DiskThresholdDeciderIT.testIndexCreateBlockIsRemovedWhenAnyNodesNotExceedHighWatermarkWithAutoReleaseEnabled

• URL: https://build.ci.opensearch.org/job/gradle-check/13720/
• CommitID: 94623f9
  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-commenter]

Codecov Report

Merging #7064 (94623f9) into main (0db20d9) will decrease coverage by 0.14%.
The diff coverage is 81.48%.

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@@             Coverage Diff              @@
##               main    #7064      +/-   ##
============================================
- Coverage     70.74%   70.61%   -0.14%     
+ Complexity    59329    59281      -48     
============================================
  Files          4825     4825              
  Lines        284369   284390      +21     
  Branches      41021    41024       +3     
============================================
- Hits         201177   200808     -369     
- Misses        66665    67059     +394     
+ Partials      16527    16523       -4     

Impacted Files	Coverage Δ
...ch/extensions/rest/RegisterRestActionsRequest.java	69.23% <54.54%> (-0.77%)	⬇️
...rch/extensions/rest/RestSendToExtensionAction.java	41.50% <100.00%> (+9.64%)	⬆️

... and 503 files with indirect coverage changes

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[vibrantvarun]

LGTM