Toolbars - hide trailing separators
Toolbars - hide trailing separators

building upon #5330 which hides leading separators

this goes through the list backwards stopping at first visible
non-separator .. and hides all separators along the way

also stops counting separators amongst visible items so that we don't
have to worry about recomputing any_visible after hiding trailing
separators
(transferred from ManageIQ/manageiq@5a16be6164dea5505fa8d003bd24f7a353216532)

ManageIQ/manageiq-ui-classic,ManageIQ/manageiq-ui-classic,ManageIQ/manageiq-ui-classic,ManageIQ/manageiq-ui-classic