[New Tab Animations] Add custom view for tab created in background

Add a custom view where the logic of the New Tab Background
animation will reside. This CL adds the custom view and a
rounded rectangle shape for the "link" icon in the animation.

Testing will be added as more logic is added in these files.

Low-Coverage-Reason: OTHER
Bug: 40282469
Change-Id: Ic88151c28d0f94fcdc303ed6d1b626275c6f675e
Reviewed-on: https://chromium-review.googlesource.com/c/chromium/src/+/6073545
Reviewed-by: Brandon Wylie <wylieb@google.com>
Reviewed-by: Calder Kitagawa <ckitagawa@chromium.org>
Commit-Queue: Dan Polanco <polardz@google.com>
Cr-Commit-Position: refs/heads/main@{#1395125}