Check new multi-instance app property for multi-instance support

- Currently, this is controlled by an allow-list, but we want to ensure
  that all apps can request to be launched in multiple instances in
  cases where SystemUI desires

Bug: 262864589
Test: atest WMShellUnitTests
Change-Id: I18c8b64c8087eb5fc237dfcfce17fe3758fb74ba