Since we have feature flagged the new user menu feature, it is
imperative we load both sets of styles until the feature has
shipped. This allows us to switch seamlessly between the two
without worrying about cached HTML being served with updated CSS.
To do this, we add a new class to both user menu's distinguishing
the legacy version from the modern version. The styles are then
scoped to these new selectors.
This also fixes some regressions with the legacy user menu in
modern Vector when wgVectorConsolidateUserLinks is disabled.
Notes:
* No caching selector is needed for #pt-userpage given it can only
ever be output for logged in users.
* ID selectors in general are bad, so scoping to mw-portlet-personal-user-menu-legacy
isolates the legacy component allowing it to be rendered alongside the modern UserMenu
Bug: T276561
Change-Id: I068c5233bb25a7b141e66a6726b5761841f83eb2
Remove redundant styles. Update personal menu dropdown to more closely reflect design of OOUI dropdown elements. Extract legcay-specific, modern-specific styles for UserMenu into separate partials. Create new shared UserMenu component.
Bug: T276561
Change-Id: I1e56cd5b3b24ac1b5cae684301b8e3a84ea33a5c
