rebase: add a stateobj variable to rebaseruntime class

The stateobj variable is an object of state.cmdstate() and will be used in
upcoming patches to clean up the logic a bit and also use cbor format to write
data to rebasestate class.

Differential Revision: https://phab.mercurial-scm.org/D3874

hgext/rebase.py

@@ -48,6 +48,7 b' from mercurial import ('
     revsetlang,
     scmutil,
     smartset,
+    state as statemod,
     util,
 )
 
@@ -184,6 +185,7 b' class rebaseruntime(object):'
         self.obsoletenotrebased = {}
         self.obsoletewithoutsuccessorindestination = set()
         self.inmemory = inmemory
+        self.stateobj = statemod.cmdstate(repo, 'rebasestate')
 
     @property
     def repo(self):