ChangesListSpecialPage: Add urlversion and make urlversion=2 ignore defaults

ChangesListSpecialPage: Add urlversion and make urlversion=2 ignore defaults

This allows us to build reliable URLs that will be consistent over time
and between users (because the defaults depend on preferences,
extension presence, etC) by using urlversion=2 and specifying the
state of each filter relative to the empty state (i.e. nothing enabled).

urlversion defaults to 1, and urlversion=1 maintains the current
behavior where the parameters are interpreted relative to the
user's default state.

Bug: T166906
Change-Id: Iaf33c14e3f909092d96453e78016814aa417673a