Summary:
Move the rust libraries and extensions to their new locations, and integrate
them with the hg-crew setup.py.
Test Plan: Run `python setup.py build` and verify rust extensions are built.
Reviewers: durham, #mercurial
Reviewed By: durham
Subscribers: fried, jsgf, mitrandir
Differential Revision: https://phabricator.intern.facebook.com/D6677251
Tasks: T24908724
Signature: 6677251:1515450235:920faf40babbce9b09e3283ff9ca328d1c5c51e6