What does this PR change? What problem does it solve?

Adds a --delete option to the restore command that deletes files from the target folder that do not exist in the snapshot. Files are only deleted if they match the --include or --exclude filters. In addition, a non-empty directory can be overwritten if the snapshots contains a file in its place.

See the documentation for more details.

Includes #4839 .

Was the change previously discussed in an issue or on the forum?

Fixes #2348

Checklist

• I have read the contribution guidelines.
• I have enabled maintainer edits.
• I have added tests for all code changes.
• I have added documentation for relevant changes (in the manual).
• There's a new file in changelog/unreleased/ that describes the changes for our users (see template).
• I have run gofmt on the code in all commits.
• All commit messages are formatted in the same style as the other commits in the repo.
• I'm done! This pull request is ready for review.