rhg: Propogate manifest parse errors instead of panicking The Rust parser for the manifest file format is an iterator. Now every item from that iterator is a `Result`, which makes error handling required in multiple new places. This makes better recovery on errors possible, compare to a run time panic. Differential Revision: https://phab.mercurial-scm.org/D11771

pub mod dirstate_map;
pub mod on_disk;
pub mod owning;
pub mod path_with_basename;
pub mod status;