Xamarin.Forms.UWP sample problems

## 🐛 Bug Report

Since I can't get the lottie animations on my XF.UWP project to work I downloaded the sources to see if the sample XF.UWP project works on my pc.

I didn't know how to run the sample projects from the solution (the sample projects don't show up as projects but as folders in my solution), so I
- created a new solution
- added the Examples.Forms and the Examples.Forms.UWP to it
- removed the project reference from Lottie.Forms and replaced it with the nuget package reference to Com.Airbnb.Xamarin.Forms.Lottie (4.0.8)

The project ran, but not all samples worked (in XF.UWP):
- play from asset or bundle -> works
- all controls -> works
- play from embedded resource -> **does not show animation**
- play from steam -> **does not show any animation**
- play from uri -> works

### Expected behavior
all samples work

### Reproduction steps
see above
### Configuration
Xamarin.Forms 4.8.0.1821
Visual Studio 16.8.3

**Version:** 4.0.8

**Platform:**
- [ ] :iphone: iOS
- [ ] :robot: Android
- [ ] :checkered_flag: WPF
- [x] :earth_americas: UWP (In case you mean XF.UWP with this flag, maybe not?)
- [ ] :apple: MacOS
- [ ] :tv: tvOS
- [x] :monkey: Xamarin.Forms

Start by opening the Examples.Forms and Examples.Forms.UWP sample projects and reproducing the embedded-resource and stream cases described in the issue under Xamarin.Forms 4.8.0.1821 and UWP. Compare them with the working asset, bundle, and URI samples; done means both failing samples display their animations.

Written by the indexing model from the issue text.