rebase: move abort() onto rebaseruntime
The function depends on a lot of the state of rebaseruntime, so it
makes sense for it to be an instance method. This will let us remove
many of the arguments to the method. That will be done in a later
patch.
Differential Revision: https://phab.mercurial-scm.org/D5392
[workspace]
members = ["hgcli", "hg-core", "hg-direct-ffi"]
exclude = ["chg"]