Integrate search-relevance functionalities with security plugin

[fen-qin]

Description

Adds search-relevance related roles to the plugin:

• read only
• full access.

Adds search-relevance system indices to demo scripts:

• .plugins-search-relevance-experiment
• .plugins-search-relevance-judgment-cache

Issues Resolved

This is a new feature for 3.1 release, no backfort

Testing

N/A

Check List

• New functionality includes testing
• New functionality has been documented
• New Roles/Permissions have a corresponding security dashboards plugin PR
• API changes companion pull request created
• Commits are signed per the DCO using --signoff

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.

[cwperks]

@fen-qin can you fix the code hygiene issues?

[cwperks]

Let's also add a CHANGELOG entry

[fen-qin]

Let's also add a CHANGELOG entry

Hello, Craig
I've addressed all comments. put the PR from draft to review. Thank you!

[DarshitChanpura]

only one comment, commas are not needed at the end of actions in the yaml file.

[fen-qin]

only one comment, commas are not needed at the end of actions in the yaml file.

Thanks, Darshit. resolve this comment

[codecov]

Codecov Report

All modified and coverable lines are covered by tests ✅

Project coverage is 72.12%. Comparing base (228744a) to head (11f2364).
Report is 1 commits behind head on main.

Additional details and impacted files

@@            Coverage Diff             @@
##             main    #5376      +/-   ##
==========================================
- Coverage   72.13%   72.12%   -0.02%     
==========================================
  Files         382      382              
  Lines       23697    23697              
  Branches     3644     3644              
==========================================
- Hits        17095    17091       -4     
- Misses       4804     4805       +1     
- Partials     1798     1801       +3     

Files with missing lines	Coverage Δ
...y/tools/democonfig/SecuritySettingsConfigurer.java	75.15% <ø> (ø)

... and 5 files with indirect coverage changes

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