Add optional --cache parameter to CLI

### Check existing issues

- [x] I've verified that this request isn't described by any existing issues.

### Request

Add an optional `--cache` parameter that takes in a path to a custom hwctl cache.

### Motivation

Adding an optional `--cache` would help in development/debugging to use caches from bug reports, for example.

Locate the hwctl CLI argument parsing and existing cache handling first. Add the optional --cache path and verify through the CLI help or relevant command that a custom cache path is accepted and used.

Written by the indexing model from the issue text.