derive: implement #[valuable] attributes

[taiki-e]

• #[valuable(rename = "...")]; derive: implement #[valuable] attributes #75
• #[valuable(transparent)]; derive: implement #[valuable] attributes #75
• #[valuable(skip)]; derive: implement #[valuable] attributes #75

[taiki-e]

As a first step, I'm planning to implement attributes like rename, skip that have non-controversial behavior and are relatively simple.

[Larandar]

This might be less trivial than it sounds, but another non-controversial would also be #[valuable(redacted)]. Almost like skip but semantically different.

[taiki-e]

I don't think we should consider that an attribute that an equivalent is no available in serde is "non-controversial" here. I cannot easily imagine how it would work.