Refactor Parser trait to pass min_indent

This removes the need to explicitly pass thru min_indent when using the parser combinators.

My ultimate goal here is to evolve the current parser closer toward a purely combinator-based parser,
at which point we can more easily transition smoothly to a formal(ish) grammar, or expand the meanings of combinators
to include things like:
* Incremental (re)parsing
* Unified parsing and formatting code
* Better error recovery
* Using the main parser directly for syntax highlighting

crates/compiler/parse/benches/bench_parse.rs

@@ -23,8 +23,9 @@ pub fn criterion_benchmark(c: &mut Criterion) {
             let (_actual, state) =
                 module::parse_header(&arena, State::new(src.as_bytes())).unwrap();
 
+            let min_indent = 0;
             let res = module_defs()
-                .parse(&arena, state)
+                .parse(&arena, state, min_indent)
                 .map(|tuple| tuple.1)
                 .unwrap();