Fix crosstalk between users for widgets hosted in lockscreen

This was initially about the Clock widget crashing repeatedly on some
devices with multiple users. Turned out that there were race conditions
when switching users that could result in remote views of one user calling
back to the RemoteViewsAdapter in keyguard that in turn sent an incorrect widget id
to a different user's widget, resulting in a crash.

Since KeyguardHostView is instantiated in the same process for different users,
it needs to carry a user identity to pass along to AppWidgetService so that
remote views services were bound to the correct user and callbacks were attached and
detached properly.

Added some aidl calls that take the userId to do the binding properly. A more
complete fix might be needed in the future so that all calls from Keyguard carry
the user id.

Also, there was a problem in comparing host uid for secondary users, since Settings
for a secondary user has a different uid than keyguard. Not an issue on single-user
systems. Changed the host.uid comparison to accomodate for the secondary user.

Bug: 7450247
Change-Id: Idbc36e3c60023cac74174f6cb7f2b2130dd3052c