Replacing IoC with .net core DI
## 🚀 Feature Requests

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### Contextualize the feature
<!--- Where does it fit in the framework and why it's being included there. --->
Many libraries starting with AutoMapper, MediatR, Ef Core, .net core IOptions and many more are providing  .net core DI registration extensions. 

To use these we should write our custom registration extensions and this is often error prone, because of the often changes in the libraries and causing incompatibilities with MvvmCross DI mechanism. Most of the ime heavry Rtti is involved. Another option we have is to provide custom IMvxIocProvider to replace default DI container of MvvmCross. But this is not very viable option because we have to support all these extensions. and very often we find various compatibility problems. Also EF Core uses scoped DbContext registration which seems is not easy to port to MvvmCross. One use case of it is when you use Medaitor pattern you can provide scoped DbContext to Handlers using constructor injection.

**Is this request feasible**? I am sure that many developers will benefit from this, but  maybe I am wrong. This is why I am opening this discussion.

### Describe the feature
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Would be very nice to be able to replace default MvvmCross DI mechanism with the default .net core DI. This would save tons of time and problems. I made several attempts to fully replace IMvxIocProvider, but facing many problems and gave up. We had discussions with several guys from Xamarin forms experiencing same problems. I am mainly WPF involved.

### Platforms affected (mark all that apply)
- [x] :robot: Android
- [x] :checkered_flag: WPF
- [x] :earth_americas: UWP
- [x] :monkey: Xamarin.Forms
