Smooth rough edges when publishing integration packages

### 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.

If you want to publish a custom integration package, there are a few gotchas you can fall foul of if you try and set things up from first principals.

- When adding a reference to your integration package from an app host, you'll need to include `IsAspireProjectResource="false"` on the `ProjectReference`
```xml

```
https://github.com/dotnet/aspire/issues/11156
- For tests, you'll likely want to use `DistributedApplicationTestingBuilder.Create()` rather than `DistributedApplicationTestingBuilder.Create`. This requires you to configure your test project to use the aspire sdk
```xml

```
This however introduces a few complications
- You'll need to specify `IsAspireProjectResource` on the `ProjectReference` to your integration project.
- `aspire update` will get confused in the future when you try to update packages. https://github.com/dotnet/aspire/issues/12053,

### Describe the solution you'd like

Some of this is documented at I'd like to see the process of publishing your own integration packages simplified.

1. Can any product changes be made to smooth out any of the above rough edges.
2. Templates
3. Documentation updates - Updating https://aspire.dev/integrations/custom-integrations/hosting-integrations/ as required based on the outcomes of this thread.

### Additional context

https://aspire.dev/integrations/custom-integrations/hosting-integrations/
https://github.com/microsoft/aspire.dev/issues/539