Use systemd-gpt-auto-generator to find boot and root partitions and reduce rdcore logic

[travier]

Describe the enhancement

We want to move the logic used to find the boot and root partitions to use systemd-gpt-auto-generator instead of custom CoreOS logic implemented in rdcore and coreos-boot-mount-generator.

Testing

• We need to make sure that we keep the current logic working for boot and root for all disk layouts (LUKS, RAID0/1, multipath, etc.)
• Verify that UUID restamping works as expected

See: https://www.freedesktop.org/software/systemd/man/latest/systemd-gpt-auto-generator.html

Related:

• Fedora bootc images tracker: https://gitlab.com/fedora/bootc/tracker/-/issues/38
• Re-enabled in bootc base images: https://gitlab.com/fedora/bootc/base-images/-/merge_requests/310
• Re-disabled in FCOS: manifests/fedora-coreos: remove systemd-gpt-auto-generator again fedora-coreos-config#3846

This heavily relates to: #2026

System details

All

Additional information

No response