Validate system authenticators names at registering.

[Thisara-Welmilla]

Issue:

• Minor improvements to the custom authentication extension product-is#23020

With this PR, verify that the registering system-defined authenticator name starts with the custom- prefix, which is reserved for user-defined authenticators, if so ignore that authenticator and add warn log.

[jenkins-is-staging]

PR builder started
Link: https://github.com/wso2/product-is/actions/runs/13307683398

[codecov]

Codecov Report

Attention: Patch coverage is 0% with 3 lines in your changes missing coverage. Please review.

Project coverage is 47.14%. Comparing base (64a8b25) to head (efd323a).
Report is 33 commits behind head on master.

Files with missing lines	Patch %	Lines
.../framework/internal/FrameworkServiceComponent.java	0.00%	3 Missing ⚠️

❌ Your patch status has failed because the patch coverage (0.00%) is below the target coverage (80.00%). You can increase the patch coverage or adjust the target coverage.

Additional details and impacted files

@@             Coverage Diff              @@
##             master    #6489      +/-   ##
============================================
- Coverage     47.15%   47.14%   -0.02%     
- Complexity    15278    15305      +27     
============================================
  Files          1747     1747              
  Lines        105380   105561     +181     
  Branches      19488    19544      +56     
============================================
+ Hits          49694    49763      +69     
- Misses        48631    48738     +107     
- Partials       7055     7060       +5     

Flag	Coverage Δ
unit	30.49% <0.00%> (-0.01%)	⬇️

Flags with carried forward coverage won't be shown. Click here to find out more.

☔ View full report in Codecov by Sentry.
📢 Have feedback on the report? Share it here.

[jenkins-is-staging]

PR builder completed
Link: https://github.com/wso2/product-is/actions/runs/13307683398
Status: failure

[jenkins-is-staging]

PR builder started
Link: https://github.com/wso2/product-is/actions/runs/13320800967

[jenkins-is-staging]

PR builder completed
Link: https://github.com/wso2/product-is/actions/runs/13320800967
Status: failure

[jenkins-is-staging]

PR builder started
Link: https://github.com/wso2/product-is/actions/runs/13321248203

[sonarqubecloud]

Quality Gate passed

Issues
0 New issues
0 Accepted issues

Measures
0 Security Hotspots
0.0% Coverage on New Code
0.0% Duplication on New Code

See analysis details on SonarQube Cloud

[jenkins-is-staging]

PR builder completed
Link: https://github.com/wso2/product-is/actions/runs/13321248203
Status: success

[jenkins-is-staging]

Approving the pull request based on the successful pr build https://github.com/wso2/product-is/actions/runs/13321248203