Fix date hardcoding in date aggregator

[sandeshkr419]

Description

Fix in date aggregator where date field was hard-coded. Fixed that to fetch from value-source if available.
This fix was included in #17165 but the PR is missed for 2.19 so creating a separate PR to only include the bug fix to be pushed to 2.19 branch as feature inclusion is blocked for now in 2.19

Will rebase #17165 after this PR gets merged.

Related Issues

Resolves #[Issue number to be closed when this PR is merged]
Fix date field hard-coding introduced in #16674 - this is required to correctly fetch date field in Date Aggregation using star-tree

Check List

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

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[owaiskazi19]

Looks good. You can remove the changes from #17165

[github-actions]

❌ Gradle check result for 5277900: 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 786bb22: UNSTABLE

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

All modified and coverable lines are covered by tests ✅

Project coverage is 71.32%. Comparing base (faabd10) to head (786bb22).
Report is 1 commits behind head on main.

Additional details and impacted files

@@             Coverage Diff              @@
##               main   #17239      +/-   ##
============================================
- Coverage     72.36%   71.32%   -1.05%     
+ Complexity    65733    64557    -1176     
============================================
  Files          5318     5318              
  Lines        305674   305676       +2     
  Branches      44349    44350       +1     
============================================
- Hits         221197   218018    -3179     
- Misses        66341    69496    +3155     
- Partials      18136    18162      +26     

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