Switch to SystemD Boot

[danirabbit]

Worth looking into SystemD boot again. I think we decided against it when distinst was being developed because it requires EFI? I guess we need to decide if non-EFI systems are now far too old to be supported

Benefits include:

• no timeout by default! No more grub timeout issues
• boot assessment: https://systemd.io/AUTOMATIC_BOOT_ASSESSMENT/

[poetfreak]

It is worth noting that some folks on newer systems refuse to use EFI simply because it is yet another unneeded attack vector and was exploited in two difernt ways in the last year. ;)

[Sandwhiched]

I'm not authorized to contribute any code here, but, one suggestion is building two ISOs for legacy BIOS and the newer standard EFI users. However, one downside I can foresee being an issue is CI/CD runtime fees if the elementary OS build system uses something like GitHub Actions.