[Minimal HUN] Use Standard Minimal HUN for Custom Views

Apps might provide custom views for headsUpContent. In the scope of Minimal HUN, we dont allow custom views.
If the app using custom headsUpContent doesnt provide title and text field, the standard template should already fall back to presenting the app name.

Bug: 336225281
Test: SystemUITests and manual
Flag: ACONFIG android.app.Flags.compact_heads_up_notification DISABLED
Change-Id: I60575757bc1812a0325627b4955137857b9ba0ae