Bump checkstyle and spotbugs

[bobbylight]

Now that we're building with Java 11 (but still generating artifacts for Java 8+), we can bump our Checkstyle and Spotbugs dependencies.

I'm taking the opportunity to add a couple of new rules and options to Checkstyle as well. This isn't a full formatting/prettifier sweep though, just low-hanging fruit.

[codecov]

Codecov Report

Attention: Patch coverage is 54.83871% with 14 lines in your changes missing coverage. Please review.

Project coverage is 80.33%. Comparing base (37af1ed) to head (25baa24).
Report is 1 commits behind head on master.

Files with missing lines	Patch %	Lines
...java/org/fife/ui/rtextarea/RTextAreaEditorKit.java	25.00%	1 Missing and 5 partials ⚠️
...org/fife/ui/rsyntaxtextarea/WrappedSyntaxView.java	0.00%	1 Missing and 3 partials ⚠️
.../org/fife/ui/rsyntaxtextarea/RSyntaxUtilities.java	0.00%	0 Missing and 3 partials ⚠️
...ife/ui/rsyntaxtextarea/focusabletip/TipWindow.java	0.00%	1 Missing ⚠️

Additional details and impacted files

@@            Coverage Diff            @@
##             master     #583   +/-   ##
=========================================
  Coverage     80.32%   80.33%           
  Complexity     7780     7780           
=========================================
  Files           178      178           
  Lines         30247    30247           
  Branches       3911     3911           
=========================================
+ Hits          24297    24299    +2     
+ Misses         4276     4274    -2     
  Partials       1674     1674           

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