Instead of passing the signer as an argument to many methods on Store, scope the Store itself to a signer.

This further allows to differentiate two different access modes on the store in radicle::cob::store::access: WriteAs (which requires signer) and ReadOnly (which does not require a signer).

The caches for issues and patches in radicle::cob::{issue,patch}::Cache are concretised by removing the first type parameter, since it was specific to issues and patches anyway. This was done in this commit as it touches very similar usage sites.

Make Device less prominent, and instead lean more heavily towards traits from the signature crate, such as Keypair and Verifier in addition to Signer. Trait bounds regarding Signer could be simplified, but this is left for the future.

In radicle-cli, the function term::cob::patches_mut, which generates errors with a hint is used instead of the lower-level Profile::patches_mut.

Commands rad issue cache and rad patch cache now construct a writeable cache on top of a read-only store.

Many knock-on changes are handled as well, to arrive at a clean state.

Changes:

• Rebase
• Fix typos