Need better way to override console configured for osie

[detiber]

Currently to override the default console for a given hardware you need to override the facility_code, such as "onprem console=ttyS0". Otherwise it will use hardcoded values based on the architecture and plan_slug.

Expected Behaviour

There should be a more straightforward way to override the console without having to resort to hacking the facility_code.

Current Behaviour

One needs to override the facility_code to add additional kernel parameters.

Possible Solution

Expose a well defined field as part of the hardware schema to override the default values for the console configuration (if not set).

Steps to Reproduce (for bugs)

1. Create a hardware definition for a machine that does not conform to the default serial configurations hardcoded in boots (such as a Macchiatobin, which is an arm64 board that uses ttyS0 for the console instead of ttyAMA0.