[Groovy -> Java/Groovy] refactor

[jrappen]

Warning

This is a WIP (work in progress). Proposed changes here will probably generate CI errors for a while.

TODO:

• fix strings
• fix tests
• go through https://docs.groovy-lang.org/latest/html/documentation/core-differences-java.html
• check against https://github.com/apache/groovy/tree/master/src/test-resources/core
• check against Remove Incompatible Regex Patterns #481
• check against [Groovy] triple quotes syntax bug #2031, [Groovy] Function default parameter value is not parsed #3518

DONE:

This PR proposes to:

• move Groovy into Java package
• Java
  • categorize operators to ease extending Java
  • move syntax variables to EOF
• Groovy
  • add RegExp (Groovy).sublime-syntax
  • add build files for Ant and GroovyC
  • add single-quoted block strings with embedded bash highlighting
  • use merge-conflict-markers (see [Common] Add git conflict marker highlighting #4047) from Java to add them to
    additional types of strings in Groovy
  • mark imports of default imports as invalid.illegal

References:

• fixes Groovy Reindent issue #654
• addresses [Regular Expression] Unified scope names for (embedded) Regular Expressions #1942
• addresses [Common] Add git conflict marker highlighting #4047
• supersedes [Groovy] refactor #4193