[Backport 2.x] Add tracking for long running SearchTask post cancellation

[ruai0511]

Description

Backport #17726

Related Issues

Resolves #[Issue number to be closed when this PR is merged]

Check List

• Functionality includes testing.
• API changes companion pull request created, if applicable.
• Public documentation issue/PR created, if applicable.

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[jainankitk]

@ruai0511 - Build is failing because of missing 3_0 version in 2.x branch:

 /home/runner/work/OpenSearch/OpenSearch/server/src/main/java/org/opensearch/tasks/TaskCancellationStats.java:38: error: cannot find symbol
        if (in.getVersion().onOrAfter(Version.V_3_0_0)) {
                                             ^
  symbol:   variable V_3_0_0
  location: class Version
/home/runner/work/OpenSearch/OpenSearch/server/src/main/java/org/opensearch/tasks/TaskCancellationStats.java:66: error: cannot find symbol
        if (out.getVersion().onOrAfter(Version.V_3_0_0)) {
                                              ^
  symbol:   variable V_3_0_0
  location: class Version
Note: Some input files use or override a deprecated API.
Note: Recompile with -Xlint:deprecation for details.
Note: Some input files use unchecked or unsafe operations.
Note: Recompile with -Xlint:unchecked for details.
2 errors

> Task :server:compileJava FAILED

[github-actions]

❌ Gradle check result for d113e83: FAILURE

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?

[andrross]

@ruai0511 No more releases are planned from the 2.x branch. Do we need this backport?

[ruai0511]

Closing this as the feature is not needed to backport to 2.x