GDScript: Improve call analysis

* Add missing `UNSAFE_CALL_ARGUMENT` warning.
* Fix `Object` constructor.
* Display an error for non-existent static methods.

modules/gdscript/tests/scripts/analyzer/warnings/unsafe_call_argument.gd

@@ -0,0 +1,37 @@
+func variant_func(x: Variant) -> void:
+	print(x)
+
+func int_func(x: int) -> void:
+	print(x)
+
+func float_func(x: float) -> void:
+	print(x)
+
+# We don't want to execute it because of errors, just analyze.
+func no_exec_test():
+	var untyped_int = 42
+	var untyped_string = "abc"
+	var variant_int: Variant = 42
+	var variant_string: Variant = "abc"
+	var typed_int: int = 42
+
+	variant_func(untyped_int) # No warning.
+	variant_func(untyped_string) # No warning.
+	variant_func(variant_int) # No warning.
+	variant_func(variant_string) # No warning.
+	variant_func(typed_int) # No warning.
+
+	int_func(untyped_int)
+	int_func(untyped_string)
+	int_func(variant_int)
+	int_func(variant_string)
+	int_func(typed_int) # No warning.
+
+	float_func(untyped_int)
+	float_func(untyped_string)
+	float_func(variant_int)
+	float_func(variant_string)
+	float_func(typed_int) # No warning.
+
+func test():
+	pass