Reduce some code duplicate with Describable interface

[jonesbusy]

Description

Reduce some code duplicate with Describable interface

Testing done

mvn clean install

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 95.00000% with 1 line in your changes missing coverage. Please review.

Project coverage is 85.02%. Comparing base (0f1c633) to head (e63c719).
Report is 2 commits behind head on main.

Files with missing lines	Patch %	Lines
src/main/java/land/oras/LayoutRef.java	66.66%	1 Missing ⚠️

Additional details and impacted files

@@             Coverage Diff              @@
##               main     #240      +/-   ##
============================================
+ Coverage     84.97%   85.02%   +0.05%     
+ Complexity      475      474       -1     
============================================
  Files            33       33              
  Lines          1597     1589       -8     
  Branches        184      181       -3     
============================================
- Hits           1357     1351       -6     
+ Misses          159      158       -1     
+ Partials         81       80       -1     

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