hash_any returns Datum, not uint32 (and definitely not "int").

The coding in JsonbHashScalarValue might have accidentally failed to fail
given current representational choices, but the key word there would be
"accidental".  Insert the appropriate datatype conversion macro.  And
use the right conversion macro for hash_numeric's result, too.

In passing make the code a bit cleaner and less repetitive by factoring
out the xor step from the switch.
Fix interval test, which was broken for floating-point timestamps.

Commit 4318daecc959886d001a6e79c6ea853e8b1dfb4b introduced a test that
couldn't be made consistent between integer and floating-point
timestamps.

It was designed to test the longest possible interval output length,
so removing four zeros from the number of hours, as this patch does,
is not ideal. But the test still has some utility for its original
purpose, and there aren't a lot of other good options.

Noah Misch suggested a different approach where we test that the
output either matches what we expect from integer timestamps or what
we expect from floating-point timestamps. That seemed to obscure an
otherwise simple test, however.

Reviewed by Tom Lane and Noah Misch.