[AutoDiff] Implement `AnyDerivative`. (#23521)
* [AutoDiff] Implement `AnyDerivative`.
Implement `AnyDerivative`, a type-erased derivative.
`AnyDerivative` forwards its operations to an arbitrary underlying base
derivative conforming to `Differentiable` and `AdditiveArithmetic`, hiding
the specifics of the underlying derivative.
Add tests.
