dirstatemap: use `set_possibly_dirty` in `clearambiguoustimes`
lets put this new method to use
Differential Revision: https://phab.mercurial-scm.org/D11121
dirstate-item: use `set_possibly_dirty` in `pure.pack_dirstate`
Lets make use of the new function.
Differential Revision: https://phab.mercurial-scm.org/D11120
dirstate-item: add a `set_possibly_dirty` method
See inline documentation for details.
The pushes the AMBIGUOUS_TIME implementation further down the line within the
DirstateItem only. When this cleanup is done we will be able to stop using this
representation internally.
Differential Revision: https://phab.mercurial-scm.org/D11119