Add and prioritize the new "_matrix/integrations/v1" widget urls

As per MSC1961, add to the whitelisted integrations_widget_urls
the new paths. This allows us to switch Scalar over to use the
new path as default.

Note, the legacy "scalar-staging.riot.im" is these days just a redirect
to scalar-staging.vector.im, so there is no addition for that. It still
needs Riot side whitelisting though for existing widgets.

Refs: matrix-org/matrix-spec-proposals#1961