Move domain state ints to DomainVerificationInfo

Hides the internal values and exposes a smaller set of defined values
for each specific case the domain verification agent might be
interested in.

These values are only for the public API output and all other classes
should continue to use the internal DomainVerificationState.

Bug: 181100856

Test: atest com.android.server.pm.test.verify.domain

Change-Id: I2b16d14bbf3a70e4c2e3f4b358af8671aed71490