[feature] Select bootloader for bare metal images

[rothgar]

With Talos 1.10 we now use systemd-boot for UEFI systems (not just secure boot) but the default build from the image factory uses the dual-boot imager option which makes very large installation ISOs.

We should make it an option to select which bootloader will be included in the iso so the file size can be reduced.

[smira]

I wonder if it should be a schematic option