fix: db-pre-config function failing with pg reserved words

When db-pre-config is accidentally set to a pg reserved word
like "true", it fails with a confusing error. The function
names should be properly quoted to avoid such errors. This commit
resolves this by quoting the pre-config function name.

Signed-off-by: Taimoor Zaeem <taimoorzaeem@gmail.com>
(cherry picked from commit a688878236)

test/io/fixtures.sql

@@ -256,3 +256,7 @@ select * from projects;
 
 create or replace view infinite_recursion as
 select * from infinite_recursion;
+
+create or replace function "true"() returns boolean as $_$
+  select true;
+$_$ language sql;