fix: update ErrorTemplate to show Exception.Message

[jonpryor]

Context: #1726
Context: #1730

Build and run `Chefs.csproj`` for e.g. net10.0-desktop and NativeAOT while using Uno 6.6.0-dev.3:

sed -i '' 's/"Uno.Sdk": ".*"/"Uno.Sdk": "6.6.0-dev.3"/g' global.json
git clean -xdf Chefs{,.Api}
dotnet publish -c Release -r osx-x64 -f net10.0-desktop -p:TargetFrameworkOverride=net10.0-desktop \
  -bl Chefs/Chefs.csproj -p:UseSkiaRendering=true -p:SkiaPublishAot=true \
  -p:SkiaPublishAot=true \
  -p:IlcGenerateMapFile=true -p:IlcGenerateMstatFile=true -p:IlcGenerateDgmlFile=true -p:IlcGenerateMetadataLog=true \
  -p:EmitCompilerGeneratedFiles=true -p:CompilerGeneratedFilesOutputPath=`pwd`/_gen
Chefs/bin/Release/net10.0-desktop/osx-x64/publish/Chefs

From the launch screen:

1. Click Skip
2. Click  Sign in with Apple
3. Click 🔍Search on the left
4. In the Search box, type m

When doing this with e838af9, the search results screen shows:

An error occurred.

…which isn't particularly helpful.

Update ErrorTemplate within FeedView.xaml to also include the Exception.Message property contents:

An error occurred:
Reflection-based serialization has been disabled for this application. Use the IServiceCollection.AddJsonTypeInfo() or IHostBuilder.UseSerialization(IHostBuilder, IEnumerable, Action) extension methods to enable JSON deserialization for type System.Collections.Generic.Dictionary2[[System.String, System.Private.CoreLib, Version=10.0.0.0, Culture=neutral, PublicKeyToken=7cec85d7bea7798e],[Chefs.Business.Models.SearchHistory, Chefs, Version=1.0.0.0, Culture=neutral, PublicKeyToken=null]]`.

The downside to this approach is that the Console log shows this message after signing in, after step (2), above:

fail: Uno.UI.DataBinding.BindingPropertyHelper[0]
      The [Message] property getter does not exist on type [Chefs.Presentation.HomeViewModel]

as well as this message after going to the 🔍Search page, after step (3), above:

fail: Uno.UI.DataBinding.BindingPropertyHelper[0]
      The [Search] property getter does not exist on type [Chefs.Presentation.SearchViewModel]

These messages appear because when ErrorTemplate is loaded, the associated DataContext is for HomeViewModel or SearchViewModel, neither of which has a Message property.

These fail messages can be ignored.

GitHub Issue (If applicable): #

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Please check if your PR fulfills the following requirements:

• Tested code with current supported SDKs
• Docs have been added/updated which fit documentation template. (for bug fixes / features)
• Unit Tests and/or UI Tests for the changes have been added (for bug fixes / features) (if applicable)
• Wasm UI Tests are not showing unexpected any differences. Validate PR Screenshots Compare Test Run results.
• Contains NO breaking changes
• Updated the Release Notes
• Associated with an issue (GitHub or internal)

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