Consolidate verify_oauth_client functions

[seanpreston]

Closes #2320

Fideslib's verify_oauth_client implementation has not been used (outside of tests) since we merged fideslib into fides. This PR removes it.

Code Changes

• Remove the fideslib version of verify_oauth_client

Pre-Merge Checklist

• All CI Pipelines Succeeded
• Documentation:
  • documentation complete, PR opened in fidesdocs
  • documentation issue created in fidesdocs
• Issue Requirements are Met
• Relevant Follow-Up Issues Created
• Update CHANGELOG.md

[codecov]

Codecov Report

Base: 88.47% // Head: 88.48% // Increases project coverage by +0.01% 🎉

Coverage data is based on head (93dccad) compared to base (0fa8359).
Patch coverage: 100.00% of modified lines in pull request are covered.

❗ Current head 93dccad differs from pull request most recent head 75ac60b. Consider uploading reports for the commit 75ac60b to get more accurate results

Additional details and impacted files

@@            Coverage Diff             @@
##             main    #2527      +/-   ##
==========================================
+ Coverage   88.47%   88.48%   +0.01%     
==========================================
  Files         328      328              
  Lines       15959    15923      -36     
  Branches     4433     4417      -16     
==========================================
- Hits        14119    14089      -30     
+ Misses       1687     1680       -7     
- Partials      153      154       +1     

Impacted Files	Coverage Δ
src/fides/lib/oauth/api/deps.py	92.85% <ø> (+2.38%)	⬆️
src/fides/lib/oauth/oauth_util.py	100.00% <100.00%> (+2.63%)	⬆️
src/fides/api/ctl/utils/errors.py	88.23% <0.00%> (-5.89%)	⬇️
src/fides/api/ops/util/oauth_util.py	93.00% <0.00%> (+6.00%)	⬆️

Help us with your feedback. Take ten seconds to tell us how you rate us. Have a feature suggestion? Share it here.

☔ View full report at Codecov.
📢 Do you have feedback about the report comment? Let us know in this issue.

[SteveDMurphy]

This all looks good to me @seanpreston - just needs the changelog update prior to merging 👍🏽