Make DialogLaunchAnimator.showFromDialog more lenient

Before this CL, calling DialogLaunchAnimator.showFromDialog from a
Dialog that was not shown using DialogLaunchAnimator (i.e. it was shown
using Dialog.show()) would crash. This CL changes that so that we show
the dialog normally instead.

Bug: 267387248
Test: DialogLaunchAnimatorTest
Change-Id: I52f475822cde1162575f6b09b0abe1c77ca132a4
(cherry picked from commit dc5b50c3)
Merged-In: I52f475822cde1162575f6b09b0abe1c77ca132a4
(cherry picked from commit 42fac0d7833a619d16f44d010f9da32fc98ece9b)
Merged-In: I52f475822cde1162575f6b09b0abe1c77ca132a4