Unify String and StringName

modules/gdscript/tests/scripts/analyzer/features/array_string_stringname_equivalent.gd

@@ -0,0 +1,8 @@
+func test():
+	# Converted to String when initialized
+	var string_array: Array[String] = [&"abc"]
+	print(string_array)
+
+	# Converted to StringName when initialized
+	var stringname_array: Array[StringName] = ["abc"]
+	print(stringname_array)

modules/gdscript/tests/scripts/analyzer/features/array_string_stringname_equivalent.out

@@ -0,0 +1,3 @@
+GDTEST_OK
+["abc"]
+[&"abc"]