GDScript: Fix STANDALONE_EXPRESSION warning for preload()

modules/gdscript/tests/scripts/parser/warnings/standalone_expression.gd

@@ -6,3 +6,16 @@ func test():
 	Vector3.ZERO
 	[true, false]
 	float(125)
+	# The following statements should not produce `STANDALONE_EXPRESSION`:
+	var _a = 1
+	_a = 2 # Assignment is a local (or global) side effect.
+	@warning_ignore("redundant_await")
+	await 3 # The `await` operand is usually a coroutine or a signal.
+	absi(4) # A call (in general) can have side effects.
+	@warning_ignore("return_value_discarded")
+	preload("../../utils.notest.gd") # A static initializer may have side effects.
+	"""
+	Python-like "comment".
+	"""
+	@warning_ignore("standalone_ternary")
+	1 if 2 else 3 # Produces `STANDALONE_TERNARY` instead.