[Rust] custom derive for struct/enum with resource types

[chenyan2002]

Currently custom derive applies to all struct and enum definitions. Understandably, the resource struct doesn't use the custom derive. The problem is that when the struct/enum type contains a resource type, the derive trait will not work. We can use additional-derive-ignore to opt-out such types individually, but that's not very convenient.

I can see several ways to fix it, but not sure which one makes more sense:

1. Only apply custom derive to struct and enum that doesn't contain resource types. This is equivalent to manually opt-out those types with additional-derive-ignore.
2. Apply the custom derive to resource struct as well. But many traits don't make sense for resource types.
3. Have a flag to define custom derive for individual types, similar to with, we can have a with-derive.

Maybe in the short term, we can apply the first option, which is also easy to implement?

[alexcrichton]

There's some additional discussion related to derive at #1386 and #812

Personally I'd prefer to avoid (1) here as it has a high risk of creating confusing situations where an end users enables derives but is confused when they're not present, not understanding the clause where it's' omitted for resource-containing-things. I understand though how other solutions are not easy and I don't have a silver bullet myself.