[Backport 2.x] Add file cache stats, reservation logic

[kotwanikunal]

Description

• Backports Include file cache stats in node stats api response #6333 and Add cache reservation logic #6350

Issues Resolved

• N/A

Check List

• New functionality includes testing.
  • All tests pass
• New functionality has been documented.
  • New functionality has javadoc added
• Commits are signed per the DCO using --signoff
• Commit changes are listed out in CHANGELOG.md file (See: Changelog)

By submitting this pull request, I confirm that my contribution is made under the terms of the Apache 2.0 license.
For more information on following Developer Certificate of Origin and signing off your commits, please check here.

[github-actions]

Gradle Check (Jenkins) Run Completed with:

• RESULT: SUCCESS ✅
• URL: https://build.ci.opensearch.org/job/gradle-check/11718/
• CommitID: 9354f73

[codecov-commenter]

Codecov Report

Merging #6485 (9354f73) into 2.x (46caaec) will increase coverage by 0.06%.
The diff coverage is 63.67%.

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@@             Coverage Diff              @@
##                2.x    #6485      +/-   ##
============================================
+ Coverage     70.27%   70.34%   +0.06%     
- Complexity    59100    59271     +171     
============================================
  Files          4796     4797       +1     
  Lines        284245   284416     +171     
  Branches      41310    41328      +18     
============================================
+ Hits         199750   200069     +319     
+ Misses        67767    67614     -153     
- Partials      16728    16733       +5     

Impacted Files	Coverage Δ
...min/cluster/stats/TransportClusterStatsAction.java	70.83% <ø> (ø)
...search/cluster/MockInternalClusterInfoService.java	0.00% <0.00%> (ø)
.../java/org/opensearch/test/InternalTestCluster.java	58.33% <12.50%> (-0.84%)	⬇️
...rch/action/admin/cluster/node/stats/NodeStats.java	48.57% <22.22%> (-1.43%)	⬇️
...rc/main/java/org/opensearch/monitor/fs/FsInfo.java	70.40% <31.25%> (-2.68%)	⬇️
...src/main/java/org/opensearch/node/NodeService.java	70.31% <33.33%> (-0.66%)	⬇️
...org/opensearch/common/settings/SettingsModule.java	83.55% <40.00%> (-0.91%)	⬇️
...c/main/java/org/opensearch/index/IndexService.java	73.87% <62.50%> (-0.68%)	⬇️
.../main/java/org/opensearch/env/NodeEnvironment.java	76.26% <68.85%> (-0.69%)	⬇️
...h/index/store/remote/filecache/FileCacheStats.java	71.18% <71.18%> (ø)
... and 520 more

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