Code Review.

[clangenb]

These are some general things that stand out to me after not having seen the code for a year. Most things concern idiomatic code, but some of them would increase readability, and therefore productivity. Not everything necessarily needs to be implemented, but could be if we touch that part of the code anyhow.

Major

• Worker: Add Error types: Introduce Error enum #253
• Add overarching ecall/ocall type: Suggestion: define only one ocall/ecall but pass an enum as arg defining the function to dispatch. #254

Minor

• Add ApiClient extension traits: Replace api-client wrappers with extension traits. #255
• Client: Move some api-client wrappers to substratee-node-primitives
• combine worker-/node-primitives in a primitives directory, i.e. primitives/node and primitives/worker
• make enclave/rpc.rs a separate crate in core
• make enclave/top_pool.rs a separate crate in core
• move enclave crypto stuff to separate crate. Started, progress here: extract crypto stuff out of enclave #361
• worker/main.rs way too big, separate it into multiple files.
• client/main.rs is also way too big.
• Remove trait UnwrapOrSgxErrorUnexpected #413
• I don't think the WorkerApi should be nested within the worker. It rather belongs to the client or primitives.
• Cleanup the Eclave_t-/u.* files by moving them in a separate directory. (Possibly lib.)
• The Stf does not make much sense to me anymore. All the methods operate on StfState anyhow. We could make Stf a trait instead of a struct and implement it for StfState. STF Design Enhancement Proposal #269

[brenzi]

@clangenb can you please go through your points and see if we can close this now?

[clangenb]

Some points are still valid and should be tackled imo.

[clangenb]

Either crossed out tasks as not so relevant or made separate issues for the remaining tasks. So closing this one.