Tracking for Aspire 9 support

[aaronpowell]

I've created https://github.com/CommunityToolkit/Aspire/milestone/1 which will track the various bits of work that is needed to integrate Aspire 9, and assigned some of the current issues to it.

As we hit things, either code that's brought over from the dotnet/aspire repo, or stuff that we have to comment out, let's create issues and add them to the milestone.

[aaronpowell]

The main branch is now using .NET Aspire 9 as the primary version to develop against.

[aaronpowell]

We're now building against the 9.0.0 GA packages for Aspire. There's a few outstanding PR's with some "last minute" integrations to tackle and then we'll cut the 9.0.0 release for the Toolkit.

@CommunityToolkit/aspire-contributors let's prioritise getting the currently open PR's done so we can aim for a release at the end of this week.

[Alirexaa]

#182 is a high priority