[FEATURE] sdboot snapshots (Tumbleweed-like)

### Pre-flight checklist

- [x] I have searched existing issues/PRs and this has not been requested before.
- [x] I have read the [Contributing Guidelines](https://github.com/CachyOS/linux-cachyos/blob/master/CONTRIBUTING.md).

### Request type

- [ ] New patch / patchset inclusion
- [ ] Kernel config change (enable/disable option)
- [ ] New kernel variant
- [ ] Scheduler tuning / addition
- [ ] Compiler / LTO / PGO optimization
- [ ] Security hardening
- [ ] Driver or hardware enablement
- [ ] Other

### Summary

Adding sdboot with OpenSuse-like snapshots handling.

### Motivation / use case

Hi dev team!

OpenSuse Tumbleweed now uses by default systemd-boot instead of Grub. Dev team have implemented a full snapper scripts suite to enable btrfs snapshots at boot, like your dev team did for Limine or Grub.

systemd-boot is light, fast, easy to set up, it can be hidden then displayed with a simple key pressure, timeout can be set to zero and increased on the fly, UI is minimal and clear, it handles BGRT so well than you can uninstall Plymouth but keep a pretty boot display (and gain some seconds at boot time)

So i guess it matches all the needs for us. I know that Peter is using it, so i wonder if CachyOS will or not provide it one day.

Thanks a lot for your answers, cheers from France!

### Patch / upstream reference (if available)

_No response_

### Testing / benchmarks

_No response_

### Additional context

_No response_