hg-core: make parse_dirstate return references rather than update hashmaps
Returing a vec is faster than updating a hashmap when the hashmap is not needed
like in `hg files` which just list tracked files.
Returning references avoid copying data when not needed improving performence
for large repositories.
Differential Revision: https://phab.mercurial-scm.org/D8861
Hello, Foobar
[b'Hello, Fo, =;:<o', b'Hello, Bar']