Support replacing UDF in-place with CREATE OR REPLACE FUNCTION

[digitalpoetry]

• [Feature] Support replacing UDF in-place with CREATE OR REPLACE FUNCTION #46122

Feature request

Is your feature request related to a problem? Please describe.
As of current, replacing a UDF is a two-step operation: DROP FUNCTION, then CREATE FUNCTION. This method involves potential downtime between the two commands for the function that is being replaced.

Describe the solution you'd like
Support syntax like

CREATE OR REPLACE FUNCTION function_name RETURNS return_type;