Move pull and push states from SyncSitesProvider to a new Redux slice#2037

gcsecsey wants to merge 20 commits intotrunkAutomattic/studio:trunkfrom

stu-711-studio-refactor-pull-and-push-states-from-syncsitesproviderAutomattic/studio:stu-711-studio-refactor-pull-and-push-states-from-syncsitesproviderCopy head branch name to clipboard