Specific Testing and AI suggested features to add

### Is there an existing issue for this?

- [x] I have searched the existing issues

### Is your feature request related to a problem? Please describe the problem.

Testing and AI have the same problem: If you want to run integartion tests on a specific project and nothing else, the entire aspire host must be run.

This results in bloat in testing because it isn't directed. We can get around things like database names by creating a new databases in our tests on the server resource, but we can't selectively run.

This is made worse for ai that is trying to help you with a project specific problem but can't just run that project because it's dependent on the entire aspire host etc so it can just run and diagnose an error.

### Describe the solution you'd like

1. In the new test framework, give us the ability to pass just the project or projects that you want to have the aspire host fire up. I.e. if there are 15 projects, I could choose 3 for an integration test between the 3. The test host should pass this to the apphost and the apphost should fire those up and all dependencies of those so that you have a complete environment for those and only those.
2. The aspire cli should be able to have a parameter that allows you to specify the projects you want it to fire up the same way.
3. It would be great to have an MCP integration in the vs code (and vs and rider) that allows the AIs to call directly to do this with information requests from aspire cli that allowed it to list all of the available resource names and then run the aspire host with mcp server only running, not the dashboard, and then it could interogate the results from the logs etc. Better is that the oltp data would be fired directly into the mcp that it could get for each project for debugging.

These 3 suggestions would go a HUGE way to improving the aspire testability story while DRASTICALLY improving AI's ability to help you with project errors that require the entire host and services.

### Additional context

_No response_