Add EarlGrey test for virtual card enrollment.

This change adds a test that triggers the virtual card enrollment after
filling with a credit card, then accepts the virtual card. This test
covers the existing behavior where the virtual card enrollment bottom
sheet closes.

Additionally, this change adds VirtualCardEnrollmentManagerTestApi to
expose clearing the virtual card enrollment strikes.

Tested: Ran 25 iterations in the simulator.

Bug: 339887700, 338634058
Change-Id: I25f82427de9002ae88d7d5c769a352b0f7be47dc
Reviewed-on: https://chromium-review.googlesource.com/c/chromium/src/+/5576915
Code-Coverage: findit-for-me@appspot.gserviceaccount.com <findit-for-me@appspot.gserviceaccount.com>
Commit-Queue: Slobodan Pejic <slobodan@chromium.org>
Reviewed-by: Sylvain Defresne <sdefresne@chromium.org>
Cr-Commit-Position: refs/heads/main@{#1328846}