refactor(tazjin/rlox): Thread through scanner errors

... and show them to users, very crudely.

Change-Id: If4491b14db1124313f6ab7e5fbfdce9fea501d11
Reviewed-on: https://cl.tvl.fyi/c/depot/+/2193
Reviewed-by: tazjin <mail@tazj.in>
Tested-by: BuildkiteCI

users/tazjin/rlox/src/errors.rs

@@ -10,6 +10,6 @@ pub struct Error {
     pub kind: ErrorKind,
 }
 
-pub fn report(loc: &str, err: &Error) {
-    eprintln!("[line {}] Error {}: {:?}", err.line, loc, err.kind);
+pub fn report(err: &Error) {
+    eprintln!("[line {}] Error: {:?}", err.line, err.kind);
 }