Add interactive UI test for uninstalling the container app.

The added test interacts with the UI in the same way that a user would
and verifies that the container app cannot be uninstalled from the
Settings app.

Additional tests will be added to verify:
* container app position for existing users
* container app preinstall ineligibility

Bug: b:331668699
Change-Id: Iaf4f783324d73e86c7377c5b37ed54c7cf4c0037
Reviewed-on: https://chromium-review.googlesource.com/c/chromium/src/+/5422377


Reviewed-by: Xiaohui Chen <xiaohuic@chromium.org>
Commit-Queue: David Black <dmblack@google.com>
Cr-Commit-Position: refs/heads/main@{#1283480}