unshelve: delete shelvedstate after a successful unshelve --continue `unshelve --continue` was preventing the deletion of `shelvedstate` on a partial `unshelve`. Ideally, `shelvedstate` should be deleted after a successful `unshelve`. Now, the behavior of `unshelve --continue` will be as follows in interactive mode: 1] The user tried to `unshelve` changes interactively but, ran into conflicts. 2] They resolved the conflicts and triggered `unshelve --continue` but, unshelved changes partially. 3] Now, on trying to do `unshelve --continue` again will abort as the last `unshelve` was successful and we are deleting the `shelvedstate`. 4] If they want to unshelve the remaining shelved change, they need to trigger `unshelve` without `--continue`. Differential Revision: https://phab.mercurial-scm.org/D6694