Make classes final where possible

Update classes that have private constructors so that they are also
declared final. In a few cases, inner-classes used private constructors
but were subclassed. These have now been changed to have package-private
constructors.

Issue gh-8945

etc/checkstyle/checkstyle-suppressions.xml

@@ -3,7 +3,6 @@
 		"-//Checkstyle//DTD SuppressionFilter Configuration 1.2//EN"
 		"https://checkstyle.org/dtds/suppressions_1_2.dtd">
 <suppressions>
-	<suppress files=".*" checks="FinalClass" />
 	<suppress files=".*" checks="InnerAssignment" />
 	<suppress files=".*" checks="InnerTypeLast" />
 	<suppress files=".*" checks="InterfaceIsType" />