Add _get_kernel_params()

[codefiles]

The kernel parameters used in _add_systemd_bootloader() and _add_efistub_bootloader() should be identical.

[svartkanin]

Looking at the efistub and systemd implementations they do have some differences

• zram
• subvols
• hsm

are we saying that those were originally missing from the efistub setup?

[codefiles]

Yes, they should be identical and are not since those are missing. This is intended to fix that and keep the code from being duplicated.

[svartkanin]

Gotcha, I see that grub also doesn't have them, are they missing there as well?

[codefiles]

The only boot loader with a fleshed out list of kernel parameters is systemd-boot. I plan to investigate application of this function to the other boot loaders. It may require additional changes to work with GRUB since by default grub-mkconfig determines the root filesystem. Other kernel parameters may be omitted due to its configuration as well.

With that said, there is nothing left to do here. This pull request is concise and is ready for merge.