Scylla doesn't allow for the types of arguments or the return type
to be frozen. As a result, before these changes, create statements
produced to restore UDFs as part of `DESCRIBE` statements could not
be executed.
We fix that and add a reproducer test and another one to verify that
the implementation is correct.
(cherry picked from commit 8582ed513b)
# Conflicts:
# cql3/functions/user_function.cc
# test/cql-pytest/test_describe.py
7f01cd7dc0