app-controls: Disable confirm button on setup open

+ Prior to this change, the confirm button was only disabled after the
user started typing a PIN.
+ This change disables the confirm button once the setup dialog is
opened.

Demo: http://screencast/cast/NTU3NDA5NjI3OTU2ODM4NHxhMjc2Y2QxNy1hZQ
Bug: b:346241877
Change-Id: I8f8271507cb6d88a33a451efa553dd318037e43a
Reviewed-on: https://chromium-review.googlesource.com/c/chromium/src/+/5615793


Commit-Queue: Amber Haynes <amberhaynes@chromium.org>
Reviewed-by: Aga Wronska <agawronska@chromium.org>
Reviewed-by: Courtney Wong <courtneywong@chromium.org>
Cr-Commit-Position: refs/heads/main@{#1312940}