mergestate: remove unnecessary recordactions() from mergestate class
This function is updating dirstate which sounds like not something which a
method on mergestate class should do. Also this just calls another function.
Lets directly call that function and remove this reducing mergestate
responsibility a bit.
There was single caller which is updated.
Differential Revision: https://phab.mercurial-scm.org/D8737
mergestate: document mergestate records in an organized way
This makes clear which mergestate record is used for what and group them based
on how they are used right now.
Differential Revision: https://phab.mercurial-scm.org/D8719