This patch backports https://github.com/scylladb/scylladb/pull/12710 to branch-5.2. To resolve the conflicts that it's causing, it also includes
* https://github.com/scylladb/scylladb/pull/12680
* https://github.com/scylladb/scylladb/pull/12681Closes#13542
* github.com:scylladb/scylladb:
uda: change the UDF used in a UDA if it's replaced
functions: add helper same_signature method
uda: return aggregate functions as shared pointers
udf: also check reducefunc to confirm that a UDF is not used in a UDA
udf: fix dropping UDFs that share names with other UDFs used in UDAs
pytest: add optional argument for new_function argument types
udt: disallow dropping a user type used in a user function
7b2215d8e0