`aspire update --self` targeted version

### 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.

Currently `aspire update --self` only allows install of a channel `stable` or `daily` and always latest.

Given that every minor release had a significant number of broken functions after the release. Therefore the `.0` release is unusable.
The CLI makes it easy to upgrade and discover the issue. But it is then unnecessary hard to downgrade to a working version.

### Describe the solution you'd like

Make downgrades of aspire CLI easier.

Either allow a new 'slow' channel (N-1 or N-2) or allow users to select a target version number.

### Additional context

If this feature is not implemented I will stop using / testing early CLI versions and wait for others to do it, because it is too much hassle.