Make opensearch_security.multitenancy.tenants.preferred configurable dynamically via security config api

[itsmevichu]

Description

• Category (Enhancement)
• Why these changes are required?
  This PR proposes making opensearch_security.multitenancy.tenants.preferred configurable dynamically via the Security configuration API in OpenSearch, instead of being solely controlled via opensearch_dashboards.yml
• What is the old behavior before changes and new behavior after changes?
  Before: preferred_tenants was not part of config APIs or /dashboardsinfo.
  After: preferred_tenants can be set via tenancy config API, is persisted in ConfigV7.Kibana, returned in /dashboardsinfo.

Issues Resolved

#5969

Testing

• Added/updated unit tests in MultiTenancyConfigApiTest and ConfigV7Test for preferred_tenants. :

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]

@itsmevichu thank you for this PR. Can you please fix the CHANGELOG conflict? Apologies for not running the checks earlier. They are running now. Please look for any failures if some of the checks come back red.

[codecov]

Codecov Report

❌ Patch coverage is 95.83333% with 2 lines in your changes missing coverage. Please review.
✅ Project coverage is 73.91%. Comparing base (1d77e46) to head (5f3f93e).
⚠️ Report is 21 commits behind head on main.

Files with missing lines	Patch %	Lines
.../dlic/rest/validation/RequestContentValidator.java	91.66%	0 Missing and 2 partials ⚠️

Additional details and impacted files

@@            Coverage Diff             @@
##             main    #5986      +/-   ##
==========================================
+ Coverage   73.82%   73.91%   +0.08%     
==========================================
  Files         439      439              
  Lines       27087    27130      +43     
  Branches     4018     4021       +3     
==========================================
+ Hits        19998    20053      +55     
+ Misses       5180     5173       -7     
+ Partials     1909     1904       -5     

Files with missing lines	Coverage Δ
...ity/dlic/rest/api/MultiTenancyConfigApiAction.java	92.78% <100.00%> (+1.87%)	⬆️
...rivileges/DashboardsMultiTenancyConfiguration.java	90.90% <100.00%> (+0.90%)	⬆️
...opensearch/security/rest/DashboardsInfoAction.java	81.03% <100.00%> (+0.33%)	⬆️
...search/security/securityconf/impl/v7/ConfigV7.java	84.28% <100.00%> (+0.11%)	⬆️
.../dlic/rest/validation/RequestContentValidator.java	89.84% <91.66%> (+3.57%)	⬆️

... and 10 files with indirect coverage changes

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[itsmevichu]

The failing CI checks seems irrelevant.