fix(trino): correctly detect parenthesized IF blocks in routine bodies

Add type annotations to the module-level constants and local counters
in the Trino dialect, and fix the `IF (a > b) THEN` vs. scalar `IF(...)`
ambiguity: an IF immediately followed by `(` is now classified as a
procedural block only when the matching closing paren is followed by
THEN, otherwise as a scalar function call. Adds a regression test for
the parenthesized condition case.

Co-Authored-By: Claude Sonnet 5 <noreply@anthropic.com>

tests/unit_tests/sql/dialects/trino_tests.py

@@ -128,6 +128,19 @@ WITH FUNCTION classify(a bigint)
     END WHILE;
     RETURN IF(a = 100, 'hundred', 'other');
   END
+SELECT classify(x) FROM some_table
+        """,
+        """
+WITH FUNCTION classify(a bigint)
+  RETURNS varchar
+  BEGIN
+    IF (a > 100) THEN
+      RETURN 'big';
+    ELSEIF a > 0 THEN
+      RETURN 'small';
+    END IF;
+    RETURN 'negative';
+  END
 SELECT classify(x) FROM some_table
         """,
     ],
@@ -135,7 +148,8 @@ SELECT classify(x) FROM some_table
 def test_inline_udf_nested_blocks(sql: str) -> None:
     """
     Test nested blocks: ``CASE ... END CASE``, ``IF ... END IF``,
-    ``WHILE ... END WHILE``, and scalar ``IF()`` function calls.
+    ``WHILE ... END WHILE``, scalar ``IF()`` function calls, and a
+    parenthesized ``IF (...) THEN`` condition.
     """
     statements = sqlglot.parse(sql.strip(), dialect=Trino)
     assert len(statements) == 1