Handle non-flat yaml settings for demo configuration detection

[derek-ho]

Description

Bug fix. Coming from: #4735, the demo config tool is not correctly detecting nested yaml for security settings when detecting whether the cluster already has security settings. This fixes it by using the SnakeYaml library to read and search for nested cases.

Issues Resolved

fix: 4735
Is this a backport? If so, please add backport PR # and/or commits #, and remove backport-failed label from the original PR.
No

Do these changes introduce new permission(s) to be displayed in the static dropdown on the front-end? If so, please open a draft PR in the security dashboards plugin and link the draft PR here
No

Testing

Existing tests pass, added a nested path test

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.

[codecov]

Codecov Report

Attention: Patch coverage is 60.00000% with 6 lines in your changes missing coverage. Please review.

Project coverage is 67.98%. Comparing base (903b7b3) to head (0471b78).
Report is 2 commits behind head on main.

Files with missing lines	Patch %	Lines
...y/tools/democonfig/SecuritySettingsConfigurer.java	60.00%	3 Missing and 3 partials ⚠️

Additional details and impacted files

@@            Coverage Diff             @@
##             main    #4793      +/-   ##
==========================================
+ Coverage   67.95%   67.98%   +0.03%     
==========================================
  Files         310      310              
  Lines       20927    20938      +11     
  Branches     3322     3326       +4     
==========================================
+ Hits        14220    14235      +15     
+ Misses       4953     4948       -5     
- Partials     1754     1755       +1     

Files with missing lines	Coverage Δ
...y/tools/democonfig/SecuritySettingsConfigurer.java	75.15% <60.00%> (-1.56%)	⬇️

... and 3 files with indirect coverage changes