feat/presentation exchange

[anwalker293]

Using locustMediatorPresentProof.py, adds presentation exchange flows and scenarios to agent.js and locustClient.py. Currently, locustMediatorPresentProof.py is written such that the presentation exchange will happen, sequentially, after receiving first a credential.

Open to making changes! Please let me know!

[anwalker293]

Important note: Verified state only checked for 5 seconds. We'll probably want to increase this

[KimEbert42]

Let us not use 5, but something like READ_TIMEOUT_SECONDS here?

[anwalker293]

Note on changes made:

• Included the variable VERIFIED_TIMEOUT_SECONDS (as opposed to READ_TIMEOUT_SECONDS, as this is already used). This is purely for checking the verified: true state. (If you want to make both the same variable, I can.) Default for the first variable is 20 seconds (can be changed upon request).
• Propagated changes we made when taking care of crashing agents.
• Made a new scenario, to match existing convention, on doing present proof with existing connections.
• Cleaned up error handling
• Put all sample commands within the docker-compose.yml. (This might need some review/recommendation on a better way to do this. As it stands, this won't work out of the box. (e.g. will have to delete the other lines))

I also verified that this works / nothing breaks by testing both of the changed scenarios. I will additionally make another, separate PR to put in the mediator message (for the 1kb test) now.