Remove GenericMock class

[ascopes]

Replace all usages of GenericMock with Mockito.mock(T...) and co. Fixes #308.

[github-actions]

Test Results

  1 604 files  ±0    1 604 suites  ±0   0s ⏱️ ±0s
23 016 tests ±0  23 003 ✔️ ±0  13 💤 ±0  0 ❌ ±0 
23 280 runs  ±0  23 267 ✔️ ±0  13 💤 ±0  0 ❌ ±0 

Results for commit 4169022. ± Comparison against base commit 7248f6f.

[codecov-commenter]

Codecov Report

Merging #341 (4169022) into main (7248f6f) will not change coverage.
The diff coverage is n/a.

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@@           Coverage Diff           @@
##             main     #341   +/-   ##
=======================================
  Coverage   78.64%   78.64%           
=======================================
  Files          91       91           
  Lines        2786     2786           
  Branches      231      231           
=======================================
  Hits         2191     2191           
  Misses        536      536           
  Partials       59       59           

Impacted Files	Coverage Δ
...hub/ascopes/jct/compilers/AbstractJctCompiler.java	100.00% <ø> (ø)
...ascopes/jct/compilers/impl/JctCompilationImpl.java	100.00% <ø> (ø)
...opes/jct/compilers/javac/JavacJctCompilerImpl.java	100.00% <ø> (ø)
...scopes/jct/repr/TraceDiagnosticRepresentation.java	100.00% <ø> (ø)
...ava/io/github/ascopes/jct/utils/IterableUtils.java	100.00% <ø> (ø)
...rc/main/java/io/github/ascopes/jct/utils/Lazy.java	100.00% <ø> (ø)