feat: added workspace oauth source for UC

[hntd187]

Description

The current providers don't cover getting tokens directly from the workspace. This PR adds that functionality.

Related Issue(s)

Documentation

https://docs.databricks.com/en/dev-tools/auth/oauth-m2m.html

[github-actions]

ACTION NEEDED

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The PR title and description are used as the merge commit message. Please update your PR title and description to match the specification.

[codecov]

Codecov Report

Attention: Patch coverage is 0% with 48 lines in your changes missing coverage. Please review.

Project coverage is 71.91%. Comparing base (4193cb0) to head (d83b8df).
Report is 2 commits behind head on main.

Files with missing lines	Patch %	Lines
crates/catalog-unity/src/credential.rs	0.00%	32 Missing ⚠️
crates/catalog-unity/src/lib.rs	0.00%	16 Missing ⚠️

Additional details and impacted files

@@            Coverage Diff             @@
##             main    #3152      +/-   ##
==========================================
- Coverage   71.98%   71.91%   -0.07%     
==========================================
  Files         137      137              
  Lines       44218    44263      +45     
  Branches    44218    44263      +45     
==========================================
+ Hits        31829    31832       +3     
- Misses      10352    10398      +46     
+ Partials     2037     2033       -4     

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[roeap]

LGTM!