Resolve #2677 : add Groovy language analyzer

[urunsiyabend]

resolves #2677

this change adds syntax recognition for .groovy, .gradle, .gvy, .gy, and .gsh files. Since universal-ctags (as of v5.9.0) doesn’t yet have a native Groovy parser, this implementation follows the same approach as Scala, using patterns plugged via Ctags.java. Once a native parser is available, it can be swapped in easily by uppercasing a single letter.

i was highly inspired by official ANTLR groovy lexer (https://github.com/apache/groovy/blob/GROOVY_3_0_X/src/antlr/GroovyLexer.g4)

lexer highlights:

• Handles all four string types: double-quoted, single-quoted, triple-double-quoted, and triple-single-quoted.
• Supports gstring interpolation: $id, ${expr}, and property chains (like $a.b.c via a dedicated GSTRING_PATH state)
• Slashy regex (/.../) and dollar-slashy regex ($/.../$) are supported. Disambiguation between regex and division is handled with a regexAllowed flag, mirroring Apache Groovy ANTLR’s REGEX_CHECK_ARRAY
• Numeric literals follow Groovy spec verbatim (hex, octal, binary, decimal, suffixes, underscores).

ctags kinds supported:
class, interface, trait, enum, annotation, method (def name(...)), field, package, import.

performance & correctness:

• tested on 2,600+ groovy and gradle files from Apache Groovy github repo (https://github.com/apache/groovy)
• Full indexing: ~5m37s
• REST search, cross-reference, and file-defs return correct symbols and highlighting.

known limitations:

• identifier rule is ASCII-only; unicode identifiers are not supported (same as other opengrok analyzers)
• non-sealed keyword in groovy 4+ splits into three tokens (non, -, sealed) because the identifier macro doesn’t span hyphens