hgweb: use parsed request to construct query parameters The way hgweb routes requests is kind of bonkers. If PATH_INFO is set, we take the URL path after the repository. Otherwise, we take the first part of the query string before "&" and the part before ";" in that. We then kinda/sorta treat this as a path and route based on that. This commit ports that code to use the parsed request object. This required a new attribute on the parsed request to indicate whether there is any PATH_INFO. The new code still feels a bit convoluted for my liking. But we'll need to rewrite more of the code before a better solution becomes apparant. This code feels strictly better since we're no longer doing low-level WSGI manipulation during routing. Differential Revision: https://phab.mercurial-scm.org/D2739