The constructor with long/int for time/tz is deprecated in favor of
Instant/ZoneId.

Update first the expectations in the tests to the new constructors, so
we know we are creating the same PersonIdents than before. We update
the code later, knowing there is no regression in e.g. format or
precision.

Change-Id: I05c759bdd4cf73b8afe79fae3c792f2f1300d1e6