anaconda container iso: add option to disable default kickstart configuration

[p5]

The ISO container installer has hard-coded Kickstart configuration which bypasses all manual configuration. While this is likely the most common use-case, there are some where we wish to still keep the manual configuration steps, and would be awesome if there was a way to enable/disable this.

The main place this would be used is when we are distributing ISO installers for others and don't necessarily need a zero-click installation, such as desktop images or smaller scale business setups where you don't require installing in bulk.

We would like to be able to allow the user to do the following:

• Create their own credentials
• Custom partitioning
• Set their language and keyboard layout
• Set the timezone
• Configure networking (hostnames, static IPs etc)

The user credentials should be easy enough (and not require any changes) - we just don't need to pass in any credentials to the osbuild configuration. The others are all hard-coded in this repo and are currently not possible to bypass.

It would be great if this option is accessible from the bootc-image-builder tools.