Improve error handling when missing required bundles

[jwakre]

Is your feature request related to a problem? Please describe. When generating an image with missing bundle dependencies, the installer does not clearly identify the missing bundle in its error messages.

Describe the solution you'd like When a bundle that is required by the installer is not listed in the .yaml config file or available in the mix, the error message should identify the missing bundle.

Additional context Users in the community are having trouble mapping installer errors to missing bundle dependencies. In the below case, the bootloader bundle was not listed in the .yaml config and the kernel-native bundle did not exist in the mix. See the community post for example error messages and logs.

https://community.clearlinux.org/t/create-mixer-image/3611

[mdhorn]

We can explore this, in both cases, the mix is missing required bundles. I'm surprised swupd didn't complain that requested bundles were not installed, or perhaps it was there but not show in the log snippet? We will have to test this, but the installer would have to rely on swupd to tell us a request bundle is not available.\