[WIP] Feat/concurrent

[naterush]

• Adds concurrent schedule replication

[naterush]

This is currently working, and w/ the addition of some tests should be good to merge. There are some future additions to this I'd like to make:

• Have a set of possible outputs classes that can be used. As of now, just integers are used but would be cool if we could also have other things as well (UTXOs).
• Have a set of possible rewrite rules to select from (not just rewriting to a random thing).

Both the above are obviously very related to each other

[naterush]

Also, currently, I don't have a functional safety oracle (and had a bit of trouble trying to design a reasonable one).

It seems like blocks and outputs are somehow a bit conflated - but maybe I'm wrong here.

[naterush]

@djrtwo thanks for the review. Refactored the functions for selecting unspent outputs and generating new outputs to make them as generic as possible (see concurrent view). Can implement others pretty easily now.

Let me know what you think would be best in regards to command line options for this...

[djrtwo]

Probably just use a --output-selection and have a dict between some string and functions.

Honestly, I just looked at protocol selection in sim/utils.py and thought.. "why do we have a select_network function". Should just be a dict...

[djrtwo]

oh and.. you going to write some tests?

[naterush]

@djrtwo good call on the dict :)

Currently, I can't test as much as I'd like. Until we get more rewrite rules (deterministic ones), it's pretty hard to test anything properly. I'd like to separate this into another PR (as it seems like a long task, and I'd like to get this merged in).

[naterush]

Merging and opening issues for test.