Fix TFM precedence issues between netX.0 and netX.0-windows* in NuGet packages

### Describe the bug

I was testing the new builds from `main` and noticed all UWP packages are broken on .NET 9:


The core of the issue is that we have a `net9.0` TFM pulling in Uno dependencies. We should not do this. The official guidance for packages that have UI framework dependencies is to have **different packages** for different UI frameworks. Uno should have their own packages as well. We need 4:
- `*.Uwp`: UWP .NET Native and .NET 9
- `*.Uwp.Uno`: UWP XAML Uno flavor
- `*.WinUI`: WinUI 3
- `*.WinUI.Uno`: WinUI 3 Uno flavor

As a **short term solution**, we can add a `net9.0-windows10.0.26100.0` TFM to work around the issue for UWP .NET 9 consumers.

### Code Platform

- [x] UWP
- [ ] WinAppSDK / WinUI 3
- [ ] Web Assembly (WASM)
- [ ] Android
- [ ] iOS
- [ ] MacOS
- [ ] Linux / GTK