since "token()" computes the token for a given partition key,
if we pass the key of the wrong type, it should reject.
in this change,
* we validate the keys before returning the "token()" function.
* drop the "xfail" decorator from two of the tests. they pass
now after this fix.
* change the tests which previously passed the wrong number of
arguments containing null to "token()" and expect it to return
null, so they verify that "token()" should reject these
arguments with the expected error message.
Fixes#10448
Signed-off-by: Kefu Chai <kefu.chai@scylladb.com>
Closes#12991