[Spring Cleanup] Remove spring dependency in client authn filter

[lashinijay]

Purpose

This PR removes dependencies and usages of the Spring framework in client authn filter

Related Issue(s)

• Remove Spring dependencies from Identity Server applications wso2/product-is#21159

[codecov]

Codecov Report

All modified and coverable lines are covered by tests ✅

Project coverage is 55.76%. Comparing base (1eb13c1) to head (2969d83).
Report is 27 commits behind head on master.

Additional details and impacted files

@@             Coverage Diff              @@
##             master    #2635      +/-   ##
============================================
- Coverage     55.76%   55.76%   -0.01%     
+ Complexity     8239     8183      -56     
============================================
  Files           632      631       -1     
  Lines         47478    47465      -13     
  Branches       8385     8384       -1     
============================================
- Hits          26477    26468       -9     
+ Misses        17211    17209       -2     
+ Partials       3790     3788       -2     

Flag	Coverage Δ
unit	38.65% <ø> (ø)

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[Thumimku]

Hi @lashinijay,

⚠️ Notice: This PR has been open for a while. To keep the repository clean and up-to-date, this PR will be closed within the next two weeks if there is no further activity.

Please take one of the following actions:

• Merge the PR if it is ready.
• Close the PR if it is no longer relevant.
• Leave a comment explaining why it should remain open and provide an update on its progress.

Your prompt attention to this matter is greatly appreciated. Thank you for your understanding and collaboration! 🙏