Checkstyle naming conventions were changed to allow most of what's in
wpimath. Naming rules were disabled completely in wpimath since almost
all suppressions are for math notation.
This also makes the Gradle build work with JDK 17.
The extra JVM args in gradle.properties works around a bug with spotless
and JDK 17: https://github.com/diffplug/spotless/issues/834
PMD.CloseResource was ignored because it's almost always a false
positive, and there are many of them.
Some valid warnings like throwing NullPointerException or using a for
loop instead of System.arraycopy() were fixed.
Abstract classes marked with PMD.AbstractClassWithoutAbstractMethod were
made concrete because they already had protected constructors.
Fixes#1697.
