Investigate ISM failures caused during 2.15 RC generation for a bug fix to remove static meta-fields

[DarshitChanpura]

During 2.15 RC generation ISM ran into integ-test failures where a warning was prominent:

[2024-06-15T03:57:00,516][WARN ][o.o.i.c.IndicesClusterStateService] [node_name_9200] [openactionit_index_1][0] marking and sending shard failed due to [failed to create index]
java.lang.NullPointerException: Cannot invoke "org.opensearch.index.mapper.MapperService.getMetadataFields()" because the return value of "org.opensearch.index.IndexService.mapperService()" is null
	at org.opensearch.security.configuration.SecurityFlsDlsIndexSearcherWrapper.<init>(SecurityFlsDlsIndexSearcherWrapper.java:65) ~[?:?]

This was root-caused to be a fix for the issue: #4349 via PR: #4349

A revert PR: #4474 was introduced to unblock 2.15. This fix is still present in 2.x line and will be included in next release unless the issue is investigated and fixed.

Expectations:

• Issue is fixed and shipped in v2.16.0
  OR
• Issue is not fixed and will have to be reverted from 2.x line until a fix is found.

--

Other relevant info:

#4474 (comment)

[stephen-crawford]

[Triage] Going to mark as triaged.