`but branch list|show` use their own version of a persisted CliId mapping

What it does is to just assign a number to each of them, and each time but branch list is run, it stores a mapping from CliId to branch name in .git/gitbutler/branch_id_map.json.

This isn't what we want, as we really don't want to create more loose files. Nor is the idea of CliIds that they must be persisted to work.

These commands should be cleaned up to use a standard CliId that can be generated from context, so persistence can be completely removed. See load_id_map and store_id_map for reference.