Clean up the Test Double generator and runtime

[sebastianbergmann]

This closes #5246, #5247, #5248, #5249, #5250, #5310, #5311, #5312, #5313, #5314, #5316, #5321, #5416, #5424, and #5536 as well as deletes now unused code and simplifies existing code.

[codecov]

Codecov Report

Attention: Patch coverage is 81.88976% with 23 lines in your changes are missing coverage. Please review.

Project coverage is 89.95%. Comparing base (36a0937) to head (bb0db02).

Files	Patch %	Lines
src/Framework/MockObject/Generator/MockBuilder.php	65.38%	18 Missing ⚠️
src/Framework/MockObject/Generator/Generator.php	90.00%	4 Missing ⚠️
...Generator/Exception/MethodNamedMethodException.php	0.00%	1 Missing ⚠️

Additional details and impacted files

@@             Coverage Diff              @@
##               main    #5697      +/-   ##
============================================
+ Coverage     89.46%   89.95%   +0.49%     
+ Complexity     6636     6512     -124     
============================================
  Files           699      687      -12     
  Lines         20073    19509     -564     
============================================
- Hits          17958    17550     -408     
+ Misses         2115     1959     -156     

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