Update the 'valhalla/type-restrictions' version of javac to generate class files with RestrictedMethod attributes.

Attribute format:

RestrictedMethod_attribute {
 u2 name_index;
 u4 length;
 u1 num_params;
 u2 restricted_param_type[num_params];
 u2 restricted_return_type;
}

'num_params' must match the number of parameters in the descriptor.

Each 'restricted_param_type' and 'restricted_return_type' must be either 0 or a descriptor string (Utf8) in the constant pool that begins with Q. The corresponding type in the descriptor must be an L type.

RestrictedType annotations:

Type annotations of the form '@RestrictedType("QPoint;")', if applied to method/constructor parameter or return types, should have the effect of generating a RestrictedMethod attribute for that method in the class file, with the corresponding `restricted_param_type` or `restricted_return_type` value given by the annotation's value. Other param/return types may also contribute strings via annotations; those without the annotation should correspond to a '0' entry in the method's RestrictedMethod attribute.

Note the alignment between descriptors and `num_params`: synthetic or implicit parameters count when deciding on the index of an annotated parameter type.

XXflattenWithTypeRestrictions mode:

If javac is invoked with argument `-XXflattenWithTypeRestrictions`, all primitive value types appearing in method signatures/returns are handled the same as primitive value types appearing as field types: the descriptor type is the reference type (`LPoint$val;`), while the RestrictedMethod attribute uses the value type (`QPoint;`).