minor: make private class final with default constructor

[Kevin222004]

minor: make private class final with default constructor

This is part of https://github.com/checkstyle/checkstyle/pull/12737

According to the https://docs.oracle.com/javase/specs/jls/se17/html/jls-8.html#jls-8.8.9 The default constructor has the same access modifier as the class. and according to the check https://checkstyle.org/config_design.html#FinalClass a class that has only private constructors and has no descendant classes is declared as final.

[Kevin222004]

Please don't merge this .

I will ping you when it is ready

[Kevin222004]

You can merge this it will fine it would be great if this get merge quicker