Enhancement: Add `--delete` option to `restore` command

The `restore` command now supports a `--delete` option that allows removing files and directories
from the target directory that do not exist in the snapshot. This option also allows files in the
snapshot to replace non-empty directories.

To check that only the expected files are deleted add the `--dry-run --verbose=2` options.

https://github.com/restic/restic/issues/2348
https://github.com/restic/restic/pull/4881