Refactor everything

Huge dump of refactored code. Still in the middle of the changes that
are to be squashed later in a one huge monster commit, because there is
no value in anything atomic here.

rottlsp/src/main.rs

@@ -37,7 +37,7 @@ impl tower_lsp::LanguageServer for RottLanguageServer {
         // Measure lexing performance to track parser responsiveness.
         let start_time = std::time::Instant::now();
         let has_errors =
-            rottlib::lexer::TokenizedFile::from_str(&params.text_document.text).has_errors();
+            rottlib::lexer::TokenizedFile::tokenize(&params.text_document.text).has_errors();
         let elapsed_time = start_time.elapsed();
 
         self.client