sql: udf already being dropped in local-legacy-schema-changer

[rharding6373]

Describe the problem

During a drop column cascade, there's an error that one of the UDFs is already being dropped.

To Reproduce

In a logic test using the local-legacy-schema-changer configuration, the following statements result in the error. The ordering and/or quantity of UDFs seems important to reproducing the error.

statement ok
CREATE TABLE t_twocol (a INT, b INT);

statement ok
CREATE FUNCTION f_unqualified_twocol() RETURNS t_twocol AS
$$
  SELECT t_twocol.a, t_twocol.b FROM t_twocol;
$$ LANGUAGE SQL;

statement ok
CREATE FUNCTION f_allcolsel_alias() RETURNS t_twocol AS
$$
  SELECT t1.a, t1.b FROM t_twocol AS t1, t_twocol AS t2 WHERE t1.a = t2.a;
$$ LANGUAGE SQL;

statement ok
CREATE FUNCTION f_tuplestar() RETURNS t_twocol AS
$$
  SELECT t_twocol.a, t_twocol.b FROM t_twocol;
$$ LANGUAGE SQL;

# This statement should be ok but fails
statement ok
ALTER TABLE t_twocol DROP COLUMN b CASCADE;

Error in output:

expected success, but found
(XXUUU) function "f_tuplestar" is already being dropped
drop_function.go:167: in dropFunctionImpl()

Expected behavior
I expect the DROP to succeed and all the functions to be dropped as part of the cascade.

Jira issue: CRDB-24090