Improve specificity with which we apply compute specs (#12773)

This makes sure we don't confuse user-controlled functions with PG's
builtin functions.

## Problem

See https://github.com/neondatabase/cloud/issues/31628

compute_tools/src/sql/add_availabilitycheck_tables.sql

@@ -3,16 +3,17 @@ BEGIN
     IF NOT EXISTS(
         SELECT 1
         FROM pg_catalog.pg_tables
-        WHERE tablename = 'health_check'
+        WHERE tablename::pg_catalog.name OPERATOR(pg_catalog.=) 'health_check'::pg_catalog.name
+        AND schemaname::pg_catalog.name OPERATOR(pg_catalog.=) 'public'::pg_catalog.name
     )
     THEN
-    CREATE TABLE health_check (
-        id serial primary key,
-        updated_at timestamptz default now()
+    CREATE TABLE public.health_check (
+        id pg_catalog.int4 primary key generated by default as identity,
+        updated_at pg_catalog.timestamptz default pg_catalog.now()
     );
-    INSERT INTO health_check VALUES (1, now())
+    INSERT INTO public.health_check VALUES (1, pg_catalog.now())
         ON CONFLICT (id) DO UPDATE
-         SET updated_at = now();
+         SET updated_at = pg_catalog.now();
     END IF;
 END
 $$