sshpeer: add support for request tracing The new 'devel.debug.peer-request' option now also display some information about request going through ssh peer.

httppeer: add support for tracing all http request made by the peer This changeset introduces a new 'devel.debug.peer-request' config. When set to True, debug message about request made by peer will be issued. This help to understand what actually happens during an exchange and tracks source of performance loss. This changeset implement support for http peer only.

httppeer: move url opening in its own method This will help adding debugging logic to request opening when investigating Mercurial performance.