refactor: custom lexer (#437)

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

Author: psteinroe

.claude/settings.local.json

@@ -0,0 +1,13 @@
+{
+  "permissions": {
+    "allow": [
+      "Bash(grep:*)",
+      "Bash(rg:*)",
+      "Bash(cargo test:*)",
+      "Bash(cargo run:*)",
+      "Bash(cargo check:*)",
+      "Bash(cargo fmt:*)"
+    ],
+    "deny": []
+  }
+}