Standardize on raised error formats

[starbelly]

Currrently, the shape of errors is non standard. In some providers a function may match on {error, Reason} and return raise Reason, others may return raise with the entire tuple.

Further, there's a lot duplicate format_error/1 clauses. Most notably are errors raised around hex operations. One idea for this in particular would be to modify rebar3_hex_client functions to take a module name and raise a provider error vs returning one. This would clean up the provider code and could provide context (i.e., it was a hex api related error) that would allow for generic format_error clauses in rebar3_hex_error/1. The only rub with that idea is we lose the context of the task (e.g., publish, retire, etc.).

Regardless, even if we have to a format clause unique to each task, we could still have some standard format_error helpers to help shrink the code if we simply provided a little more context about the error. For example we could standardize on ?RAISE(task, hex, Error}), thus at the very least we would know it's a hex api related error and safely reach out to a error format helper.