[java] Provide example rulesets for customized naming conventions

[adangel]

Description:

Similar quickstart.xml, we could provide naming convention rulesets, preconfigured with different defaults:

• minimum length of field names, variables names, class names, constants
• allowed characters
• camel case, casing
• https://google.github.io/styleguide/javaguide.html#s5-naming
• https://www.oracle.com/technetwork/java/codeconventions-135099.html
• http://cr.openjdk.java.net/~alundblad/styleguide/index-v6.html#toc-naming

This could be extended for other languages as well.

While the rules are configurable, it might not be so easy to adjust the rules without having examples.
See also #2266 .

[oowekyala]

I think we could add an "example config" element to document rules, which would scale better than exposing and maintaining new rules references. Checkstyle does this very well, eg https://checkstyle.org/config_header.html#Header_Examples

[adangel]

Good idea!