Optional ethcore features should be enabled by default

[tomusdrw]

Recently some parts for ethcore and ethcore-miner were made optional: see #9020

However, we import ethcore and ethcore-miner crate from multiple places, an all of those places should specify the required features. It is however easly forgotten.

We should make the features default, and other crates that don't require them should just include the crate with no-default-features.

Also using the features if they are disabled should trigger an error. Currently 2.0 and 2.1 just silently fail to work correctly. Seems that work-notify, price-info and stratum are just broken currently.

[tomusdrw]

My bad, it seems that the features are set up correctly, although work-notify is the only one broken, see:
https://github.com/paritytech/parity/pull/9020/files#r201957185

That said I still believe that the features should be on by default. It never makes sense to compile Parity without them, it should only be used as an optimization feature for crates dependent on ethcore.