securityadmin: Replace TransportClient by RestHighLevelClient

[rs-eliatra]

Description

[Describe what this change achieves]

• Category = Maintenance
• Why these changes are required?
  Check description in: Replace uses of deprecated TransportClient #1578

Issues Resolved

#1578

Testing

Testing done:

• unit testing
• manual tests

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[codecov-commenter]

Codecov Report

Merging #1638 (8081472) into main (fc3842c) will decrease coverage by 0.55%.
The diff coverage is 50.00%.

@@             Coverage Diff              @@
##               main    #1638      +/-   ##
============================================
- Coverage     64.61%   64.05%   -0.56%     
+ Complexity     3217     3212       -5     
============================================
  Files           247      249       +2     
  Lines         17352    17478     +126     
  Branches       3082     3087       +5     
============================================
- Hits          11212    11196      -16     
- Misses         4594     4723     +129     
- Partials       1546     1559      +13     

Impacted Files	Coverage Δ
...g/opensearch/security/support/WildcardMatcher.java	61.03% <ø> (ø)
...a/org/opensearch/security/tools/SecurityAdmin.java	45.55% <38.46%> (-2.18%)	⬇️
...opensearch/security/filter/SecurityRestFilter.java	76.66% <66.66%> (+0.80%)	⬆️
...opensearch/security/rest/SecurityWhoAmIAction.java	78.37% <78.37%> (ø)
.../action/configupdate/ConfigUpdateNodeResponse.java	86.36% <83.33%> (-1.14%)	⬇️
...arch/security/rest/SecurityConfigUpdateAction.java	95.23% <95.23%> (ø)
.../opensearch/security/OpenSearchSecurityPlugin.java	81.00% <100.00%> (+0.07%)	⬆️
...rity/action/configupdate/ConfigUpdateResponse.java	100.00% <100.00%> (ø)
...mazon/dlic/auth/http/jwt/HTTPJwtAuthenticator.java	9.43% <0.00%> (-75.48%)	⬇️
...ava/com/amazon/dlic/auth/ldap2/MakeJava9Happy.java	39.13% <0.00%> (-4.35%)	⬇️
... and 13 more

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[cliu123]

@rs-eliatra @nibix 1.3 branch has been created to hold all changes for 1.3 branch. This PR will be included in 2.0 branch, so main is the right target branch.

[cliu123]

Removing the label backport 1.3 because TransportClient is removed from OpenSearch 2.0.

[peternied]

@cliu123 Is there a reason we do not want this change in 1.3? Seems like it will more than make the pencils down date

[cliu123]

@cliu123 Is there a reason we do not want this change in 1.3? Seems like it will more than make the pencils down date

This change is not necessary for 1.3.0 since TransportClient still exists in 1.3.0. This PR is a part of removing TransportClient effort. There will be more PRs to be done, for example #1660. 1.3.0 code freeze is being targeted for next week, I think it will be safer to only merge things that have been completely settled down to 1.3.0 : ). But removing TransportClient is still not done yet.