wireproto: don't expose legacy commands to version 2 of wire protocol Now that we have the ability to control which transports a wire protocol command is exposed on, let's put it to use. We flag the "branches," "changegroup," and "changegroupsubset" commands as only available on version 1. "branches" was used by the legacy discovery mechanism and was replaced by the "known" and "heads" commands. "changegroup" and "changegroupsubset" were replaced by "getbundle." "between" is also legacy. However, since it is used by the SSH handshake protocol, marking it as legacy is a bit more complicated and will be done in a later commit. Another nuanced issue with this change is that the server-advertised capabilities still list "changegroupsubset" despite the command not being available. This will be addressed in a subsequent commit. Differential Revision: https://phab.mercurial-scm.org/D2485