tests/BasicTest: Use java.time constructors for PersonIdent

Stop using the deprecated constructor with long/int for time/tz and
use instead Instant/ZoneId.

The code is still using the old constructor, but this verifies that we
are creating identical instances. We will update the code later.

Change-Id: I3844bf1e790e53e69a894cd697bddb31b755c2e6