Introduce DI ADType

The ADType can wrap a different ADType and signifies that the DI implementation of the wrapper function for that ADType will be used rather than the native backend ADType This would solve an important need where packages can't currently distinguish between an intention to directly call a corresponding ad tool vs the di wrapper for said tool. Having this would enable the ability to use, test, and consequently validate/benchmark the two (fixing issues with both usages). cc @gdalle