Support anonymous request token auth for GHCR

[jonesbusy]

Description

Should fix #178

Testing done

CI and enable test that was ignored

Submitter checklist

• I have read and understood the CONTRIBUTING guide
• I have run mvn license:update-file-header, mvn spotless:apply, pre-commit run -a, mvn clean install before opening the PR

[codecov]

Codecov Report

Attention: Patch coverage is 87.50000% with 1 line in your changes missing coverage. Please review.

Project coverage is 84.87%. Comparing base (787f863) to head (b3502c9).
Report is 2 commits behind head on main.

Files with missing lines	Patch %	Lines
src/main/java/land/oras/Registry.java	50.00%	0 Missing and 1 partial ⚠️

Additional details and impacted files

@@             Coverage Diff              @@
##               main     #180      +/-   ##
============================================
+ Coverage     84.07%   84.87%   +0.80%     
- Complexity      332      335       +3     
============================================
  Files            29       29              
  Lines          1162     1164       +2     
  Branches        112      113       +1     
============================================
+ Hits            977      988      +11     
+ Misses          128      122       -6     
+ Partials         57       54       -3     

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