Deep Stubs Incompatible With Mocking Enum

[AndreasTu]

Mockito can't mock abstract enums in Java 15 or later because they are now marked as sealed.
So Mockito reports that now with a better error message.

If a deep stub returns an abstract enum, it uses in the error case now the first enum literal of the real enum.

Fixes #2984

[codecov-commenter]

Codecov Report

Attention: 5 lines in your changes are missing coverage. Please review.

Comparison is base (b6554b2) 85.34% compared to head (b4bea3e) 85.33%.

Files	Patch %	Lines
...on/bytebuddy/InlineDelegateByteBuddyMockMaker.java	37.50%	4 Missing and 1 partial ⚠️

Additional details and impacted files

@@             Coverage Diff              @@
##               main    #3167      +/-   ##
============================================
- Coverage     85.34%   85.33%   -0.01%     
  Complexity     2911     2911              
============================================
  Files           334      334              
  Lines          8866     8867       +1     
  Branches       1099     1101       +2     
============================================
  Hits           7567     7567              
- Misses         1007     1008       +1     
  Partials        292      292              

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[AndreasTu]

@TimvdLippe I have fixed your remarks. And I have also moved the spotless code into gradle/spottless.gradle to activate the spotless checks also in the new java21 subproject.

[TimvdLippe]

Couple of nits in the test and let's do the spotless work in a different PR and apply to all subprojects. Most likely that will cause a bit more reformatting.

[TimvdLippe]

Thanks!