[Backport 2.x] [Manual] Added insecureString options to allow to easier migration (#5496)

[kartg]

Description

Manual backport of #5496 to 2.x

Signed-off-by: Chris White chriswhite199@gmail.com
(cherry picked from commit 0b775e7)

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: FAILURE ❌
• URL: https://build.ci.opensearch.org/job/gradle-check/17737/
• CommitID: 97fe1f1
  Please examine the workflow log, locate, and copy-paste the failure(s) below, then iterate to green.
  Is the failure a flaky test unrelated to your change?

[kotwanikunal]

#1703 is back :(

[github-actions]

Gradle Check (Jenkins) Run Completed with:

• RESULT: UNSTABLE ❕
• TEST FAILURES:

      1 org.opensearch.search.SearchWeightedRoutingIT.testStrictWeightedRoutingWithCustomString

• URL: https://build.ci.opensearch.org/job/gradle-check/17780/
• CommitID: 97fe1f1
  Please review all flaky tests that succeeded after retry and create an issue if one does not already exist to track the flaky failure.

[codecov]

Codecov Report

Merging #8094 (97fe1f1) into 2.x (a8420a2) will decrease coverage by 0.02%.
The diff coverage is 84.61%.

@@             Coverage Diff              @@
##                2.x    #8094      +/-   ##
============================================
- Coverage     70.66%   70.64%   -0.02%     
+ Complexity    56822    56800      -22     
============================================
  Files          4702     4702              
  Lines        268992   269002      +10     
  Branches      39767    39769       +2     
============================================
- Hits         190078   190032      -46     
- Misses        62533    62629      +96     
+ Partials      16381    16341      -40     

Impacted Files	Coverage Δ
.../org/opensearch/common/settings/SecureSetting.java	74.62% <84.61%> (+9.71%)	⬆️

... and 479 files with indirect coverage changes