Create thread id to SourceLookup map

[jed326]

Description

This PR includes changes to retrieve SourceLookup based on the current thread id. See #17743 (comment) for more details.

Testing

This PR includes new test coverage on the cache case, as well as the existing scripting tests passing.
More broadly we need to invest in better perf testing related to scripting: opensearch-project/opensearch-benchmark-workloads#362

Related Issues

Relates #17743

Check List

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

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[github-actions]

❌ Gradle check result for 501d8f9: 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?

[sohami]

By adding new API we are not preventing any other usage of the existing API to fall into the same trap and the assumption here is that this FieldScript will only be used in the fetch phase. Instead as discussed, lets add the map with threadId to SourceLookup in the SearchLookup class to create SourceLookup per threadId. Also from the source method we will return the source lookup from the map to make the usage of SourceLookup consistent from within SearchLookup

[github-actions]

❌ Gradle check result for eea1ced: 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 9248b29: 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 c0f5565: 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?

[jed326]

Gradle check failing on this:

Cannot mock/spy class org.apache.lucene.index.LeafReaderContext
Mockito cannot mock/spy because :
 - final class
org.mockito.exceptions.base.MockitoException: 
Cannot mock/spy class org.apache.lucene.index.LeafReaderContext
Mockito cannot mock/spy because :
 - final class
	at __randomizedtesting.SeedInfo.seed([1791A3DB61DA55EA:558FD8B43BECCA70]:0)
	at org.opensearch.script.ScriptServiceTests.testScriptsUseCachedSourceLookup(ScriptServiceTests.java:197)

[jed326]

I'm a little confused on this one as the mockito version we're on (5.16) is supposed to be able to mock final classes. Will go with an alternative approach for now while I look into that.

[github-actions]

❕ Gradle check result for 42ae9a0: 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.