[Backport] [2.x] Adds mock implementation for TelemetryPlugin (#8357)

[Gaganjuneja]

Description

Backport to 2.x
Main PR - #8357
Commit - 5fd49d0

[github-actions]

Gradle Check (Jenkins) Run Completed with:

• RESULT: FAILURE ❌
• URL: https://build.ci.opensearch.org/job/gradle-check/19248/
• CommitID: 6a33073
  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:

      1 org.opensearch.indices.replication.SegmentReplicationIT.testReplicationPostDeleteAndForceMerge

• URL: https://build.ci.opensearch.org/job/gradle-check/19249/
• CommitID: dc57671
  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 #8481 (dc57671) into 2.x (7f6bc0d) will increase coverage by 0.00%.
The diff coverage is 100.00%.

@@            Coverage Diff            @@
##                2.x    #8481   +/-   ##
=========================================
  Coverage     70.56%   70.57%           
+ Complexity    57104    57089   -15     
=========================================
  Files          4746     4746           
  Lines        270451   270451           
  Branches      39931    39931           
=========================================
+ Hits         190850   190877   +27     
+ Misses        63246    63159   -87     
- Partials      16355    16415   +60     

Impacted Files	Coverage Δ
server/src/main/java/org/opensearch/node/Node.java	85.77% <100.00%> (+1.09%)	⬆️

... and 462 files with indirect coverage changes