Support variable expressions in parenthesis

[jevanlingen]

What's changed?

Nested parentheses around variable expressions are supported as well for the groovy parser.
Also added the tests for method invocation with nested parentheses (but disabled).

What's your motivation?

• Groovy parser does not correctly handle nested parenthesis #4703
• Gradle parser fails with extra parens around an expression #4615

Checklist

• I've added unit tests to cover both positive and negative cases
• I've read and applied the recipe conventions and best practices
• I've used the IntelliJ IDEA auto-formatter on affected files

[jevanlingen]

This was just a bug in the parser, the visitVariableExpression should also use the visitVariableExpression so things like:

def timestamp(int hours, int minutes, int seconds) {
  (hours) * 60 * 60 + (minutes * 60) + seconds
}

starts working!

[timtebeek]

Thanks a lot! Great to have this fix pulled in already, and the added tests to know what still needs work.