wireprotoserver has generic and version 1 server code. The wireproto
module also has both version 1 and version 2 command implementations.
Upcoming work I want to do will make it difficult for this code to
live in the current locations. Plus, it kind of makes sense for the
version 2 code to live in an isolated module.
This commit copies the HTTPv2 bits from wireprotoserver into a new
module. We do it as a file copy to preserve history. A future
commit will be copying wire protocol commands into this module
as well. But there is little history of that code, so it makes
sense to take history for wireprotoserver.
nit: should we (as a cleanup step) rename this to something that doesn't sound like it means RFC7540?