dirstate: drop the now unused magic constants for the dirstate module
We no longer need them for the dirstate logic. We only need them in the
dirstate map (and parsers) logic.
This smell like progress.
Differential Revision: https://phab.mercurial-scm.org/D10964
dirstate: move the handling of special case within the dirstatemap
The dirstatemap is as well, if not better, suited to decided how to encode the
various case. So we move the associated code in the dirstatemap `addfile`
method.
This means the dirstate no longer need to know about the various magic value
used in the dirstate V1 format.
The pain of the messy API start to be quite palpable in Rust, we should clean
this up once the current large refactoring is dealt with.
Differential Revision: https://phab.mercurial-scm.org/D10963