Fixing the Engine specific files from INDEX_STORE_HYBRID_NIO_EXTENSIONS list to make sure engine files are getting mmapped

[navneet1v]

Description

This PR includes:

1. Fixing the Engine specific files from INDEX_STORE_HYBRID_NIO_EXTENSIONS list to make sure engine files are getting mmapped.
2. Fixing the backward incompatible changes in ScoreScript class. [Feature] Expose term frequency in Painless script score context OpenSearch#9081

For 1, Core team introduced a change which resulted in deprecating the setting: INDEX_STORE_HYBRID_MMAP_EXTENSIONS, hence as the setting was deprecated the unit tests were failing with error, as warnings were getting generated.

2> REPRODUCE WITH: ./gradlew ':test' --tests "org.opensearch.knn.index.KNNSettingsTests.testGetSettingValueDefault" -Dtests.seed=45E93CD93802AAC7 -Dtests.security.manager=false -Dtests.locale=ar-LB -Dtests.timezone=Asia/Tehran -Druntime.java=11
  2> java.lang.AssertionError:
    Expected: a collection containing "[index.store.hybrid.mmap.extensions] setting was deprecated in OpenSearch and will be removed in a future release! See the breaking changes documentation for the next major version."

With this change we are removing the .vec and .vex file(Engine specific files) from INDEX_STORE_HYBRID_NIO_EXTENSIONS to make sure that .vec and .vex files are getting mmaped. As per the documentation , if file extensions are not present in INDEX_STORE_HYBRID_NIO_EXTENSIONS they will be Mmapped.

Files list on node after the change

"index": {
					"store": {
						"hybrid": {
							"nio": {
								"extensions": [
									"segments_N",
									"write.lock",
									"si",
									"cfe",
									"fnm",
									"fdx",
									"fdt",
									"pos",
									"pay",
									"nvm",
									"dvm",
									"tvx",
									"tvd",
									"liv",
									"dii",
									"vem"
								]
							}
						}
					}
				},

Files list on node before the change

Issues Resolved

#995

Check List

• New functionality includes testing.
  • All tests pass
• New functionality has been documented.
  • New functionality has javadoc added
• Commits are signed as per the DCO using --signoff

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[noCharger]

The changes for Fixing the backward incompatible changes in ScoreScript class. https://github.com/opensearch-project/OpenSearch/pull/9081 looks good to me