refactor: custom lexer

[psteinroe]

• adds a new tokenizer crate that turns a string into simple tokens
• adds a new lexer + lexer_codegen that uses the tokeniser to lex into a new SyntaxKind enum

the new implementation is

• much more performant (no extra string allocations, no call to C library)
• works with broken strings (!!!!)
• custom-made to our use-case (eg the LineEnding variant comes with a count)

in a follow-up, we will be able to:

• parse custom parameters that popular tools use
• pre-process to remove unsupported stuff
• parse non-sql content (e.g. commands) via a simple custom parser

todos:

• use new lexer in splitter
• make sure we support all the different parameter formats popular tools use -> will do it in a follow-up
• tests