Add minmode configuration

Adds a config_minmode_available to check if minmode is available on the device.

Flag: com.android.systemui.enable_minmode
Bug: 425665402
(cherry picked from https://googleplex-android-review.googlesource.com/q/commit:35ec16dfdbbcc87e4a8d99b38063e18f3f782f94)
(cherry picked from https://googleplex-android-review.googlesource.com/q/commit:080c6efa79d77276fb05a3ba1b18ac7ce3918b57)
Merged-In: I87ce51d9c4bf17b684eba34bc6018e7c247abb8e
Change-Id: I87ce51d9c4bf17b684eba34bc6018e7c247abb8e