infinitepush: introduce server option to route every push to bundlestore This patch introduces a new config option for server `infinitepush.pushtobundlestore` which if sets to True, the server will route each incoming push to the bundlestore and store all the parts i.e. changegroups, phases, obsmarkers in the bundlestore and won't be applied to the revlog. This config option does not need any client side wrapping and does not need any custom bundle2 part or stream level parameter to decide where the push should go. This is very useful for Mozilla CI use case where they have a central server that recieves pushes to trigger code-reviews, trigger a test run of CI, run static analysis etc. The server using the new config option can stash standalone bundles to the bundlestore and server can get access to individual revisions on demand. A new test file which has related tests are added for the config option. Differential Revision: https://phab.mercurial-scm.org/D2958