merge: pass mergeresult obj in _forgetremoved() (API)
Instead of returning a dict of actions and then updating it, let's pass the
object directly and update it there.
This makes `updateactions()` on mergeresult unused and this patch removes that.
After this patch, we have couple of methods left on mergeresult class which
still exposes the internal dict based action storage.
Differential Revision: https://phab.mercurial-scm.org/D8889