wireproto: use CBOR for command requests Now that we're using CBOR in the new wire protocol, let's convert command requests to it. Before I wrote this patch and was even thinking about CBOR, I was thinking about how commands should be issued and came to the conclusion that we didn't need separate frames to represent the command name from its arguments. I already had a partially completed patch prepared to merge the frames. But with CBOR, it makes the implementation a bit simpler because we don't need to roll our own serialization. The changes here are a bit invasive. I tried to split this into multiple commits to make it easier to review. But it was just too hard. * "command name" and "command argument" frames have been collapsed into a "command request" frame. * The flags for this new frame are totally different. * Frame processing has been overhauled to reflect the new order of things. * Test fallout was significant. A handful of tests were removed. Altogether, I think the new code is simpler. We don't have complicated state around receiving commands. We're either receiving command request frames or command data frames. We /could/ potentially collapse command data frames into command request frames. Although I'd have to think a bit more about this before I do it. Differential Revision: https://phab.mercurial-scm.org/D2951