Mark domain verify declaring app testOnly

Allows non-root shell to disable the component/package, so that the
test works on userdebug devices.

Also makes the package test use disable-user, which works without
testOnly, to cover more disable cases and potentially narrow down
similar issues in the future if testOnly ever breaks.

Bug: 187005090

Test: CtsDomainVerificationDeviceTestCases
Test: CtsDomainVerificationHostTestCases

Change-Id: I4eed82e0d6036308c550b1c1abd2dc66fdcdd643