Feature request: create symlinks to latest snapshots

I saw another topic about grub-btrfs and I thought it would be easier to simply have symlinks to the last `n` snapshots. Then it is easy to have a static grub menu to select them. It is of course possible to manually change the kernel command line, but guessing the snapshot names using long date format isn't so easy.

IMHO I'd like to have the last 5 hourly/manual snapshots plus last 5 dailys, but this should be configurable.

The issue names no files or tests; start by locating the snapshot creation and configuration entry points. Define how configurable hourly/manual and daily retention counts map to symlink targets, and verify that the resulting links support a static GRUB menu.

Written by the indexing model from the issue text.