PG-417: Replace 'CREATE OR REPLACE' with 'CREATE' for extension.

While analyzing the pg_stat_monitor installation scripts I found several
vulnerabilities. pg_stat_monitor uses CREATE OR REPLACE to install its
functions which is a security hazard. An attacker can precreate the functions
have a superuser install the extension and after installation the attacker
can switch out the function with a malicious version since he would still
be the owner of the function. Instead of CREATE OR REPLACE the installation
script should use plain CREATE to prevent this attack.

For reference
https://www.postgresql.org/docs/current/extend-extensions.html#EXTEND-EXTENSIONS-SECURITY
https://github.com/timescale/pgspot

pg_stat_monitor--1.0.13.sql.in

@@ -89,7 +89,7 @@ RETURNS SETOF record
 AS 'MODULE_PATHNAME', 'pg_stat_monitor'
 LANGUAGE C STRICT VOLATILE PARALLEL SAFE;
 
-CREATE OR REPLACE FUNCTION get_state(state_code int8) RETURNS TEXT AS
+CREATE FUNCTION get_state(state_code int8) RETURNS TEXT AS
 $$
 SELECT
 	CASE
@@ -102,7 +102,7 @@ SELECT
 $$
 LANGUAGE SQL PARALLEL SAFE;
 
-CREATE or REPLACE FUNCTION get_cmd_type (cmd_type INTEGER) RETURNS TEXT AS
+CREATE FUNCTION get_cmd_type (cmd_type INTEGER) RETURNS TEXT AS
 $$
 SELECT
 	CASE
@@ -225,7 +225,7 @@ SELECT
 $$
 LANGUAGE SQL PARALLEL SAFE;
 
-CREATE OR REPLACE FUNCTION histogram(_bucket int, _quryid text)
+CREATE FUNCTION histogram(_bucket int, _quryid text)
 RETURNS SETOF RECORD AS $$
 DECLARE
  rec record;

pg_stat_monitor--1.0.14.sql.in

@@ -89,7 +89,7 @@ RETURNS SETOF record
 AS 'MODULE_PATHNAME', 'pg_stat_monitor'
 LANGUAGE C STRICT VOLATILE PARALLEL SAFE;
 
-CREATE OR REPLACE FUNCTION get_state(state_code int8) RETURNS TEXT AS
+CREATE FUNCTION get_state(state_code int8) RETURNS TEXT AS
 $$
 SELECT
 	CASE
@@ -102,7 +102,7 @@ SELECT
 $$
 LANGUAGE SQL PARALLEL SAFE;
 
-CREATE or REPLACE FUNCTION get_cmd_type (cmd_type INTEGER) RETURNS TEXT AS
+CREATE FUNCTION get_cmd_type (cmd_type INTEGER) RETURNS TEXT AS
 $$
 SELECT
 	CASE
@@ -226,7 +226,7 @@ SELECT
 $$
 LANGUAGE SQL PARALLEL SAFE;
 
-CREATE OR REPLACE FUNCTION histogram(_bucket int, _quryid text)
+CREATE FUNCTION histogram(_bucket int, _quryid text)
 RETURNS SETOF RECORD AS $$
 DECLARE
  rec record;

pg_stat_monitor--1.0.sql.in

@@ -86,7 +86,7 @@ RETURNS SETOF record
 AS 'MODULE_PATHNAME', 'pg_stat_monitor'
 LANGUAGE C STRICT VOLATILE PARALLEL SAFE;
 
-CREATE OR REPLACE FUNCTION get_state(state_code int8) RETURNS TEXT AS
+CREATE FUNCTION get_state(state_code int8) RETURNS TEXT AS
 $$
 SELECT
 	CASE
@@ -99,7 +99,7 @@ SELECT
 $$
 LANGUAGE SQL PARALLEL SAFE;
 
-CREATE or REPLACE FUNCTION get_cmd_type (cmd_type INTEGER) RETURNS TEXT AS
+CREATE FUNCTION get_cmd_type (cmd_type INTEGER) RETURNS TEXT AS
 $$
 SELECT
 	CASE
@@ -212,7 +212,7 @@ SELECT
 $$
 LANGUAGE SQL PARALLEL SAFE;
 
-CREATE OR REPLACE FUNCTION histogram(_bucket int, _quryid text)
+CREATE FUNCTION histogram(_bucket int, _quryid text)
 RETURNS SETOF RECORD AS $$
 DECLARE
  rec record;