style: do not suppress `this-escape`

[vil02]

This PR includes this-escape into the active compiler warnings. The changes in the *.java files are minimal.

Continuation of #5165.

• [x] I have read CONTRIBUTING.md.
• [x] This pull request is all my own work -- I have not plagiarized it.
• [x] All filenames are in PascalCase.
• [x] All functions and variable names follow Java naming conventions.
• [x] All new algorithms have a URL in their comments that points to Wikipedia or other similar explanations.
• [x] All new code is formatted with clang-format -i --style=file path/to/your/file.java

[codecov-commenter]

Codecov Report

All modified and coverable lines are covered by tests :white_check_mark:

Project coverage is 38.56%. Comparing base (324969f) to head (44626c7).

Additional details and impacted files

@@             Coverage Diff              @@
##             master    #5166      +/-   ##
============================================
- Coverage     38.57%   38.56%   -0.02%     
+ Complexity     2379     2378       -1     
============================================
  Files           516      516              
  Lines         15313    15313              
  Branches       2957     2957              
============================================
- Hits           5907     5905       -2     
- Misses         9121     9122       +1     
- Partials        285      286       +1     

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