Support secondary_user_on_secondary_display on CtsAppEnumerationTestCases

secondary_user_on_secondary_display is for background users that have
access to UI on assigned displays (a.k.a. visible background users) on
devices that have config_multiuserVisibleBackgroundUsers enabled.
The main use case is Automotive's multi-display Whole Cabin experience
where passengers (modeled as visible background users) can interact
with the display in front of them concurrently with the driver
(modeled as the the current user) interacting with driver's display.

Fixes include
- Add the secondary_user_on_secondary_display metadata.
- Add user_id to 'cmd notification' shell command for the proper user.

Bug: 369937065
Flag: TEST_ONLY
Test: atest CtsAppEnumerationTestCases
      atest --user-type secondary_user_on_secondary_display CtsAppEnumerationTestCases
(cherry picked from https://partner-android-review.googlesource.com/q/commit:357cbf5830fa907f0d41be7cf2a9b2693c2fa42c)
(cherry picked from https://googleplex-android-review.googlesource.com/q/commit:3290b6c2deafbb8aa6af2f3ab1a7cd91283094c4)
Merged-In: I3c44e94acfd2e1698c37814ee6b77ec729a3f68e
Change-Id: I3c44e94acfd2e1698c37814ee6b77ec729a3f68e
2 files changed