Update to .NET 8.0, Avalonia 11.0.9 and fix launcher issue

[AnErrupTion]

• Update to .NET 8.0
• Update to Avalonia 11.0.9
• Don't load MosaSettings again in BaseLauncher.cs and MosaCompiler.cs as they're already initialized by the caller; and make sure they're actually initialized everywhere (e.g. in UnitTestSystem.cs)
• Delete unused backup C# project files

[charsleysa]

Missing some changes, the Directory.Build.props file needs to be updated as well as korlib

[AnErrupTion]

Missing some changes, the Directory.Build.props file needs to be updated as well as korlib

The props file is already updated, maybe you didn't see it? Also, Korlib doesn't need to be updated (just like the other BareMetal projects) because it uses the Mosa.BareMetal.targets file, which should itself use the target framework set in Directory.Build.props.

[charsleysa]

Sorry, don't know how I missed that the Directory.Build.props file was already updated.

In regards to korlib, I believe this line has to be updated to match the dotnet version

MOSA-Project/Source/Mosa.Korlib/Mosa.Korlib.csproj

Line 10 in 2eeffe4

<AssemblyVersion>7.0.0.0</AssemblyVersion>

[charsleysa]

LGTM

[AnErrupTion]

In regards to korlib, I believe this line has to be updated to match the dotnet version

Oh yeah I forgot about the assembly version! It's not technically required to update it, but it makes things more consistent. Thanks! It's updated now :D