[Pull-based ingestion] Emit lag metric for pull-based ingestion poller

[yupeng9]

Description

Emit lag metric for pull-based ingestion poller

Also update the API of message to return the timestamp of the message

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[github-actions]

❌ Gradle check result for 8934cb8: FAILURE

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[github-actions]

❌ Gradle check result for 7763c5b: FAILURE

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[github-actions]

❌ Gradle check result for 7763c5b: 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?

[github-actions]

❌ Gradle check result for 7133033: 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?

[github-actions]

❌ Gradle check result for 7133033: 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?

[github-actions]

❌ Gradle check result for dd41a8b: FAILURE

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[github-actions]

✅ Gradle check result for dd41a8b: SUCCESS

[codecov]

Codecov Report

Attention: Patch coverage is 80.95238% with 4 lines in your changes missing coverage. Please review.

Project coverage is 72.47%. Comparing base (54e02a7) to head (46dd86f).
Report is 6 commits behind head on main.

Files with missing lines	Patch %	Lines
...rch/indices/pollingingest/DefaultStreamPoller.java	25.00%	2 Missing and 1 partial ⚠️
...pensearch/plugin/kinesis/KinesisShardConsumer.java	50.00%	0 Missing and 1 partial ⚠️

Additional details and impacted files

@@            Coverage Diff            @@
##               main   #17977   +/-   ##
=========================================
  Coverage     72.47%   72.47%           
- Complexity    67034    67086   +52     
=========================================
  Files          5478     5478           
  Lines        310132   310155   +23     
  Branches      45087    45092    +5     
=========================================
+ Hits         224775   224792   +17     
- Misses        66960    67023   +63     
+ Partials      18397    18340   -57     

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[mch2]

lgtm, small changelog format typo

[github-actions]

✅ Gradle check result for 46dd86f: SUCCESS