New Patcher instance to remove problem enum values from the shadowed jspecify NullMarked class

[jtduffy]

Resolves #2976

Adds a new Patcher instance that runs during the shadowJar task that removes ElementType.MODULE and ElementType.RECORD_COMPONENT from the @target annotation on the shaded jspecify NullMarked class.
Both enum values were introduced after Java 8 and cause ArrayStoreException in Java 8's AnnotationParser
when Spring scans the agent JAR because of the presence of the shaded Caffeine v3 jar.

Also adds a README that summarizes every Patcher instance's functionality.

[codecov-commenter]

Codecov Report

✅ All modified and coverable lines are covered by tests.
✅ Project coverage is 70.84%. Comparing base (4576cc4) to head (2862f8c).
⚠️ Report is 4 commits behind head on main.

Additional details and impacted files

@@             Coverage Diff              @@
##               main    #2982      +/-   ##
============================================
+ Coverage     70.83%   70.84%   +0.01%     
- Complexity    10667    10672       +5     
============================================
  Files           873      873              
  Lines         42960    42970      +10     
  Branches       6501     6503       +2     
============================================
+ Hits          30429    30443      +14     
- Misses         9596     9598       +2     
+ Partials       2935     2929       -6     

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