[WIP] Output concurrency

[ingrinder]

This is an early WIP draft for allowing output concurrency - i.e. entry output can occur before all entries have instantiated, building on the multithreading support. This is something I've had lying around for a few months and got round to rebasing onto current master.

@HorlogeSkynet what do you think of this approach so far? I probably won't get the idea finished for a while. Particularly I thought about putting 923990c in its own PR but I may as well put it in this draft for now.

P.S. this PR will probably get force pushed at some point when rebasing on master again.

I forgot to add the no integrations tag to my commits, my bad!

Description

• Refactors the way output works in entries slightly - now uses a getter on a property for each entry, which seemed cleaner than the current solution passing output back to a method.
• Adds a lot of stuff in Output. It's a bit of a mess, still.

Reason and / or context

Often the IP and GPU entries take a little longer on my system, getting faster feedback is nice 😄

How has this been tested ?

Only locally run so far.

Types of changes :

• Bug fix (non-breaking change which fixes an issue)
• Typo / style fix (non-breaking change which improves readability)
• New feature (non-breaking change which adds functionality)
• Breaking change (fix or feature that would cause existing functionality to change)

Checklist :

• [IF NEEDED] I have updated the README.md file accordingly ;
• [IF NEEDED] I have updated the test cases (which pass) accordingly ;
• [IF BREAKING] This pull request targets next Archey version branch ;
• My changes looks good ;
• I agree that my code may be modified in the future ;
• My code follows the code style of this project (PEP8).