refactor: common base library (#1780)

## Description

This adds a new crate `iroh_base`. The following types were moved into
the new crate:

* `Hash`, `HashAndFormat` and `BlobFormat` from `iroh_bytes::util`
* `base32` encoding/decoding util functions. They lived at various
places before.
* `RpcError` and `RpcResult` from `iroh_bytes::util`

## Notes & open questions

* Naming: Shall it be `iroh_common` or `iroh_base`? I do not mind. If
anyhow has a preference, please raise. I can change easily.
* Anything else that should be moved over? Anything that I moved that
should *not* be moved?

## Change checklist

- [ ] Self-review.
- [ ] Documentation updates if relevant.
- [ ] Tests if relevant.

---------

Co-authored-by: Asmir Avdicevic <asmir.avdicevic64@gmail.com>

Cargo.toml

@@ -2,6 +2,7 @@
 members = [
   "iroh",
   "iroh-bytes",
+  "iroh-base",
   "iroh-gossip",
   "iroh-metrics",
   "iroh-net",