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/cli/src/format.rs

@@ -157,7 +157,9 @@ fn parse_all<'a>(arena: &'a Bump, src: &'a str) -> Result<Ast<'a>, SyntaxError<'
     let (module, state) = module::parse_header(arena, State::new(src.as_bytes()))
         .map_err(|e| SyntaxError::Header(e.problem))?;
 
-    let (_, defs, _) = module_defs().parse(arena, state).map_err(|(_, e, _)| e)?;
+    let (_, defs, _) = module_defs()
+        .parse(arena, state, 0)
+        .map_err(|(_, e, _)| e)?;
 
     Ok(Ast { module, defs })
 }