Update Uno.Wasm.Bootstrap to latest version 7.x

[Arlodotexe]

Background

In CommunityToolkit/Labs-Windows#297, we updated all Uno libraries to the latest version, except for Uno.Wasm.Bootstrap.

According to the Uno Platform team:

Uno.Wasm.Bootstrap 3.x is .NET6, and is using emscripten 2.0.23: https://github.com/unoplatform/Uno.Wasm.Bootstrap/blob/fc89b40db92a14b8f04d4c5c9c72690bdcd7b878/src/Uno.Wasm.Bootstrap/Constants.cs#L19

Uno.Wasm.Bootstrap 7.x is .NET7, and is using emscripten 3.1.12: https://github.com/unoplatform/Uno.Wasm.Bootstrap/blob/55a871e6ed4a255a93631f75d9edb6362356adbe/src/Uno.Wasm.Bootstrap/Constants.cs#L19

During CommunityToolkit/Labs-Windows#297, we found that Rive.RiveSharp could not be used with Uno.Wasm.Bootstrap 3.x as it was compiled with another version. This was corrected in CommunityToolkit/Labs-Windows#306 and Rive now works with the latest version of all other Uno packages.

The problem

Labs is still using Uno.Wasm.Bootstrap 3.x, but needs to be using the latest version.

Prerequisites

• Rive.RiveSharp needs to be compatible with emscripten 3.1.12 before we can update Uno.Wasm.Boostrap.

[Arlodotexe]

This is also blocking our investigation into fixing the Rive experiment in Release mode on WASM.

[michael-hawker]

Related to rive-app/rive-sharp#4

CommunityToolkit/Labs-Windows#328 was failing to update to SkiaSharp.Views.WinUI 2.88.3 (with enscripten updates) due to mono/SkiaSharp#2272

So I think this means we need to wait until we update the Windows App SDK references in CommunityToolkit/Labs-Windows#183 or for a SkiaSharp update?

[Arlodotexe]

I've updated us to the latest version of SkiaSharp. Testing in a codespace, I'm seeing this error:

Exception Encountered Loading file 'ms-appx:///SourceAssets/CanvasLayout/samples/CanvasLayout.Samples/CanvasLayout.md':
The file [/SourceAssets/CanvasLayout/samples/CanvasLayout.Samples/CanvasLayout.md] cannot be found
   at Windows.Storage.Helpers.AssetsManager.DownloadAsset(CancellationToken ct, String assetPath) in /home/vsts/work/1/s/src/Uno.UWP/Storage/Helpers/AssetsManager.wasm.cs:line 88
   at Windows.Storage.StorageFile.GetFileFromApplicationUri(CancellationToken ct, Uri uri) in /home/vsts/work/1/s/src/Uno.UWP/Storage/StorageFile.wasm.cs:line 30
   at Windows.Foundation.AsyncOperation`1.<BuildTaskAsync>d__5[[Windows.Storage.StorageFile, Uno, Version=255.255.255.255, Culture=neutral, PublicKeyToken=null]].MoveNext() in /home/vsts/work/1/s/src/Uno.Foundation/AsyncOperation.TResult.cs:line 47
   at System.WindowsRuntimeSystemExtensions.<AsTaskCore>d__11`1[[Windows.Storage.StorageFile, Uno, Version=255.255.255.255, Culture=neutral, PublicKeyToken=null]].MoveNext() in /home/vsts/work/1/s/src/Uno.UWP/System.Runtime/WindowsRuntimeSystemExtensions.cs:line 66
   at CommunityToolkit.Labs.Shared.Renderers.ToolkitDocumentationRenderer.GetDocumentationFileContents(ToolkitFrontMatter metadata) in /workspaces/Labs-Windows/common/CommunityToolkit.Labs.Shared/Renderers/ToolkitDocumentationRenderer.xaml.cs:line 186

Putting this aside for now, will investigate in more detail later.