Query table_comments without unrolling with UNION ALL

`table_comments` is equally "hard" for the engine as
`information_schema.columns`. Avoid optimizing the query on the `dbt`
side by sending `UNION ALL` with individual schemas. Let the engine
figure out the optimal strategy.

.changes/unreleased/Under the Hood-20231003-161428.yaml

@@ -0,0 +1,7 @@
+kind: Under the Hood
+body: Query table_comments without unrolling with UNION ALL
+time: 2023-10-03T16:14:28.238801+02:00
+custom:
+  Author: findepi
+  Issue: ""
+  PR: "357"

dbt/include/trino/macros/catalog.sql

@@ -67,7 +67,6 @@
 
 
 {% macro trino__get_catalog_table_comment_schemas_sql(information_schema, schemas) -%}
-    {%- for schema in schemas %}
     select
         catalog_name as "table_database",
         schema_name as "table_schema",
@@ -79,11 +78,7 @@
         and
         schema_name != 'information_schema'
         and
-        schema_name = '{{ schema | lower }}'
-    {%- if not loop.last %}
-    union all
-    {% endif -%}
-    {%- endfor -%}
+        schema_name in ('{{ schemas | join("','") | lower }}')
 {%- endmacro %}