[v4] Add promisified wrapper for stateManager

[s1na]

One of the main sources of asynchrony in VM is the state manager. This wrapper allows us to slowly shift towards promises without having to modify the whole codebase at once. E.g. a new part that's being modernized could wrap its stateManager like this:

const state = new StateManager()

const pstate = new PStateManager(state)
await pstate.getAccount(addr)

This is a temporary class and will have to be deleted when the whole codebase has transitioned to promises.

(Will be merged into #479)

[holgerd77]

That's a great approach and also looks good! 👍

[coveralls]

Coverage remained the same at 95.126% when pulling 60d3cc1 on promisified-state into 256fe59 on v4.

[holgerd77]

Maybe we just merge this into master instead of v4 and release this with v3, then others can also use this to prepare for a transition? Since this is not breaking/touching anything at all and is just the additional preparatory class/base layer?

[s1na]

To be honest I haven't tested this as thoroughly. What do you think about this approach:

Maybe we could start with non-breaking changes in #479, and every once in a while port the changes back to master for v3.x releases, e.g. when the initial refactoring round stabilizes a bit, we can merge back and release v3.1.

But of course, as you mentioned, since this is not touching any code, and it's opt-in (they have to explicitly import the file) there shouldn't be any problem with merging right now.

Whatever you think best.

[holgerd77]

Ok, then let's go on with the 3.1 approach, think this is generally a solid ground to continue.