Rename resource sharing feature flag to the non-experimental key

[DarshitChanpura]

Description

Resource sharing graduates out of experimental in opensearch-project/security#6348, which drops the experimental. segment from the feature-flag settings with no deprecated fallback:

Before	After
plugins.security.experimental.resource_sharing.enabled	plugins.security.resource_sharing.enabled
plugins.security.experimental.resource_sharing.protected_types	plugins.security.resource_sharing.protected_types

Updates the integTest cluster settings in build.gradle to the new keys.

Only the setting strings change. The ConfigConstants constant names (OPENSEARCH_RESOURCE_SHARING_ENABLED, OPENSEARCH_RESOURCE_SHARING_PROTECTED_TYPES) are unchanged, so no Java/Kotlin references are affected. The gradle -Dresource_sharing.enabled system property that gates the resource-sharing CI matrix is a separate toggle and is left as is.

Because the rename has no fallback, the security integTest jobs here will fail to start a node (unknown setting [plugins.security.resource_sharing.enabled]) until a new 3.9 security snapshot publishes. Security PR 6348 is merged, so that republish is the only remaining gate; this needs to land in 3.9 with it.

Related Issues

Companion to opensearch-project/security#6348. Related to opensearch-project/security#4500

Check List

• New functionality includes testing.
• New functionality has been documented.
• API changes companion pull request created.
• Commits are signed per the DCO using --signoff.
• Public documentation issue/PR created.

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[codecov]

Codecov Report

✅ All modified and coverable lines are covered by tests.
✅ Project coverage is 68.44%. Comparing base (e3ec711) to head (25a77e5).

❌ Your project check has failed because the head coverage (68.44%) is below the target coverage (75.00%). You can increase the head coverage or adjust the target coverage.

Additional details and impacted files

@@             Coverage Diff              @@
##               main    #1815      +/-   ##
============================================
- Coverage     68.60%   68.44%   -0.17%     
+ Complexity     3751     3749       -2     
============================================
  Files           417      417              
  Lines         20888    20888              
  Branches       2189     2189              
============================================
- Hits          14331    14297      -34     
- Misses         5457     5492      +35     
+ Partials       1100     1099       -1     

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[riysaxen-amzn]

Approving. Verified against the PR head:

• New keys match ConfigConstants in Graduate resource sharing feature out of experimental security#6348 exactly: plugins.security.resource_sharing.enabled and plugins.security.resource_sharing.protected_types.
• Full-repo grep for experimental.resource_sharing returns nothing after this change.
• Unlike the alerting counterpart (Rename resource sharing feature flag to the non-experimental key alerting#2231), no IT here references the cluster setting by name. ResourceSharingIT.java only reads the resource_sharing.enabled system property, and security-test-workflow.yml only passes -Dresource_sharing.enabled=true, so the single build.gradle hunk is the complete change.

Good to merge once the security integTest jobs pick up a 3.8 snapshot containing 6348.