CBM should provide ability to list and switch between custom and distro kernels

[seanvk]

Describe the bug
When running a custom kernel which has been installed with its own entry file, it would be nice to be able use cbm cli to list all kernels including custom entries as well as be able to at least switch between.

Additional context
Similar to #194 and #205 this is a request to improve workflow with custom kernels on Clear.

[dorileo]

Thank you @seanvk I'm adding this to my todo list.