automation: update packages in requirements files We like keeping up to date. The content of the autogenerated files changed slightly because I used a newer version of `pip-compile` than what was used previously. Differential Revision: https://phab.mercurial-scm.org/D6714

automation: install latest Python versions This required bumping the pyenv commit so the new versions are available. Differential Revision: https://phab.mercurial-scm.org/D6713

upgrade: introduce the internal code for revlog cloning selection For now we still clone every single revlogs but all the selection mechanism is now in place in the lower layer. The next changesets will introduce the user interface part of the selection.