Port the NATS configuration file lexer from Go's conf/lex.go to C#.
The lexer is a state-machine tokenizer that supports the NATS config
format: key-value pairs with =, :, or whitespace separators; nested
maps {}; arrays []; single and double quoted strings with escape
sequences; block strings (); variables $VAR; include directives;
comments (# and //); booleans; integers with size suffixes (kb, mb, gb);
floats; ISO8601 datetimes; and IP addresses.
