Simplify user flow for setting default supervisor as PO

A follow up CL will clean up and separate the DeviceAdminAdd and
ProfileOwnerAdd logic (see b/131713071)

Bug: 124066840
Test: manual (overlay config_defaultSupervisionProfileOwnerComponent and
confirm only that component can be set as profile owner after setup is
complete)
Test: manual (install CtsVerifier, adb shell am start -n "com.android.cts.verifier/.admin.tapjacking.OverlayingActivity", user should not be able to click the "Allow" button)

Change-Id: Iccd931801145719110ce75421c35db80ea651779