[CVC Dialog][VCN][Android] Always show custom icons for virtual cards

Always show custom icon for virtual cards on the Card Unmask prompt.
Currently it is only shown if the AutofillEnableCardArtImage flag is
enabled. It is enabled by adding a boolean argument `showCustomIcon`
to AutofillUiUtils::getCardIcon which enables callers to specify if the
custom icon should be fetched.

Bug: 1417919
Change-Id: I6cc6ab66c842e2fd67bba053e4adcf619c313bab
Reviewed-on: https://chromium-review.googlesource.com/c/chromium/src/+/4335449
Reviewed-by: Friedrich Horschig <fhorschig@chromium.org>
Reviewed-by: Florian Leimgruber <fleimgruber@google.com>
Commit-Queue: Vishwas Uppoor <vishwasuppoor@google.com>
Cr-Commit-Position: refs/heads/main@{#1119983}