[Backport 2.x] Allow MockTracingTelemetry to await for asynchronous tasks termination before validating spans

[opensearch-trigger-bot]

Backport 0274095 from #9561.

[github-actions]

Compatibility status:

Checks if related components are compatible with change d167e16

Incompatible components

Incompatible components: [https://github.com/opensearch-project/cross-cluster-replication.git, https://github.com/opensearch-project/performance-analyzer.git]

Skipped components

Compatible components

Compatible components: [https://github.com/opensearch-project/security.git, https://github.com/opensearch-project/alerting.git, https://github.com/opensearch-project/index-management.git, https://github.com/opensearch-project/anomaly-detection.git, https://github.com/opensearch-project/asynchronous-search.git, https://github.com/opensearch-project/sql.git, https://github.com/opensearch-project/observability.git, https://github.com/opensearch-project/common-utils.git, https://github.com/opensearch-project/job-scheduler.git, https://github.com/opensearch-project/reporting.git, https://github.com/opensearch-project/k-nn.git, https://github.com/opensearch-project/geospatial.git, https://github.com/opensearch-project/ml-commons.git, https://github.com/opensearch-project/notifications.git, https://github.com/opensearch-project/neural-search.git, https://github.com/opensearch-project/performance-analyzer-rca.git, https://github.com/opensearch-project/security-analytics.git]

[github-actions]

Gradle Check (Jenkins) Run Completed with:

• RESULT: FAILURE ❌
• URL: https://build.ci.opensearch.org/job/gradle-check/23869/
• CommitID: d167e16
  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: SUCCESS ✅
• URL: https://build.ci.opensearch.org/job/gradle-check/23873/
• CommitID: d167e16

[codecov]

Codecov Report

Merging #9646 (d167e16) into 2.x (945c4b5) will increase coverage by 0.14%.
Report is 1 commits behind head on 2.x.
The diff coverage is 78.50%.

@@             Coverage Diff              @@
##                2.x    #9646      +/-   ##
============================================
+ Coverage     70.74%   70.89%   +0.14%     
- Complexity    57629    57751     +122     
============================================
  Files          4769     4770       +1     
  Lines        272600   272705     +105     
  Branches      40132    40147      +15     
============================================
+ Hits         192853   193323     +470     
+ Misses        63281    62766     -515     
- Partials      16466    16616     +150     

Files Changed	Coverage Δ
...a/org/opensearch/action/search/SearchResponse.java	88.42% <70.00%> (-1.21%)	⬇️
...org/opensearch/search/GenericSearchExtBuilder.java	73.84% <73.84%> (ø)
...ensearch/action/search/SearchResponseSections.java	97.43% <100.00%> (+1.13%)	⬆️
...search/search/internal/InternalSearchResponse.java	100.00% <100.00%> (ø)

... and 479 files with indirect coverage changes