Expanding Any derive to provide more features automatically

[udoprog]

The Any derive should be expanded to provide the following glue code automatically:

Getters and setters for any fields which are pub, and not explicitly marked as #[any(skip)].

Constructor glue so that the type can be constructed in Rune with syntax appropriate for the type.

For example:

#[derive(Any)]
struct Npc {
    x: i64,
    y: i64,
}

#[derive(Any)]
struct Point(i64, i64);

Can be constructed like this in Rune (unless any field is marked as non-public or #[any(skip)]):

let npc = Npc { x: 10, y: 10 };
let p = Point(20, 40);

Note: this would be implementation by using a generated constructor and mapping the appropriate constructor syntax in Rune using CompileMeta to this constructor.

Checklist

• Generating getters and setters for field not marked with #[any(skip)].
• Generating constructors and mapping them in the Rune compiler through CompileMeta.
  • For tuple types.
  • For struct types.
  • For enum types (tuple and struct variants).