Related to: #14242#14243 14293
Variants passed to LookupContext#find() seem to be ignored, so
I've used the setter instead: `finder.variants = [ variant ]`.
I've also added some more test cases for variants. Hopefully this
time passing tests will mean it actually works.
Take variants into account when calculating template digests in
ActionView::Digest.
Digestor#digest now takes a hash as an argument to support variants and
allow more flexibility in the future. Old-style arguments have been
deprecated.
Fixes#14242