[Clean Up] Clean OIDC session code v1

[Thumimku]

Proposed changes in this pull request

1. Log is a static final variable, so it should be "LOG" not "log".
2. Clean some un used code.
3. Checking for debug enabled is redundent, but improve performance if the logging message contains computations. But if there is no computations, no concatinations then checking debug enabled affect the performance. Hence I selectively remove debug enabled checks if the message is simple.

[codecov]

Codecov Report

Attention: Patch coverage is 0% with 50 lines in your changes missing coverage. Please review.

Project coverage is 55.14%. Comparing base (69881de) to head (6303c3c).
Report is 32 commits behind head on master.

Files with missing lines	Patch %	Lines
...n/backchannellogout/DefaultLogoutTokenBuilder.java	0.00%	16 Missing ⚠️
...y/oidc/session/handler/OIDCLogoutEventHandler.java	0.00%	16 Missing ⚠️
...session/backchannellogout/LogoutRequestSender.java	0.00%	12 Missing ⚠️
...c/session/backchannellogout/ClaimProviderImpl.java	0.00%	6 Missing ⚠️

Additional details and impacted files

@@             Coverage Diff              @@
##             master    #2621      +/-   ##
============================================
- Coverage     55.24%   55.14%   -0.10%     
- Complexity     8260     8300      +40     
============================================
  Files           632      632              
  Lines         47943    48644     +701     
  Branches       7867     7980     +113     
============================================
+ Hits          26484    26825     +341     
- Misses        17630    17950     +320     
- Partials       3829     3869      +40     

Flag	Coverage Δ
unit	38.68% <0.00%> (-0.02%)	⬇️

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[jenkins-is-staging]

PR builder started
Link: https://github.com/wso2/product-is/actions/runs/11766728732

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PR builder completed
Link: https://github.com/wso2/product-is/actions/runs/11766728732
Status: success

[jenkins-is-staging]

Approving the pull request based on the successful pr build https://github.com/wso2/product-is/actions/runs/11766728732