Get referrences from OCI Layout

[jonesbusy]

WIP. Not finished

Description

Testing done

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 3 lines in your changes missing coverage. Please review.

Project coverage is 85.05%. Comparing base (0ab5e5e) to head (04ac9f2).
Report is 2 commits behind head on main.

Files with missing lines	Patch %	Lines
src/main/java/land/oras/OCILayout.java	84.21%	1 Missing and 2 partials ⚠️

Additional details and impacted files

@@             Coverage Diff              @@
##               main     #245      +/-   ##
============================================
+ Coverage     84.72%   85.05%   +0.32%     
- Complexity      469      477       +8     
============================================
  Files            33       33              
  Lines          1578     1599      +21     
  Branches        174      178       +4     
============================================
+ Hits           1337     1360      +23     
+ Misses          162      159       -3     
- Partials         79       80       +1     

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