Merges in rain's accountswitcher trick (flip getCanUseMultiAccountMobile
and canUseMultiAccountNotifications) as an opt-in toggle alongside the
existing custom account manager, default on.
Also fixes SidebarPatcher.js, which referenced window.bunny - that
global doesn't exist on Vendetta/Revenge (only Bunny), so the sidebar
pin threw on load there. Swapped to @vendetta/metro's findByProps/
findByName, matching every other lookup already in this plugin.
