strip: rename test-mq-strip into test-strip And makes it use the strip extension only (except for the part testing mq interaction)

mq: extract strip function as its standalone extension (issue3824) Strip now lives in its own extension reminder: The extension is surprisingly called `strip`. The `mq` extension force the use of the strip extension when its enabled. This is both necessary for backward compatibility (people expect `mq` to comes with strip) and become some utility function used by `mq` are now in the strip extension.

strip: move the strip helper function for mq to strip The next patch finally move the command. No joke! (hey, this is for issue3824)

strip: move checklocalchanges from mq to strip One more step for issue3824.

strip: move checksubstate from mq to strip One more step for issue3824

mq: prepare a strip extension for extraction Strip will lives in its own extension. The extension is surprisingly called `strip`. (as discussed in issue3824) The `mq` extension force the use of the strip extension when its enabled. This will both necessary for backward compatibility (people expect `mq` to comes with strip) and become some utility function used by `mq` will move in the strip extension.

histedit: remove unused parents() call

mq: have the strip command functionnal on repo without mq This is the last step before being able to extract `strip` in its own extension. The changes are made in mq to allow a move only extraction without touching a line of code.

mq: extract `mq.queue.strip` It does not depend on `mq.queue` anymore.

mq: drop the use of mq.queue.qparent in mq.queue.strip Same as in the previous changeset, rev is never `None`. We can just copy the two relevant lines in in `queue.strip`. This help having `queue.strip` independent from `queue`. One further step toward the extraction of `strip` in an independent extension. (As discussed in issue3824).