split from #16077 to improve non web rendering issues

we did few disablement at https://github.com/checkstyle/checkstyle/pull/16126/files

updates required (highly recommend to do all following sub tasks in separate PRs):

• enable xml plugin in pom.xml, disabled due to dependency: bump org.apache.maven.plugins:maven-site-plugin from 3.12.1 to 3.21.0 #15799 (comment) , check if this case will be violated Issue #14019: Kill mutation for writeFileError #16467 (comment) . New xsd - https://maven.apache.org/xsd/site-2.0.0.xsd
• fix links in sun and Google style, remove them from suppression that we did in first PR
• in logs there are huge amount of WARNINGS like: Anchor name "Description" used more than once, Anchor name "Properties" used more than once, .... moved to site log has a lot of warnings 'Anchor name "Description" used more than once' #17531