Make runner reusable

[joelamouche]

Two issues were preventing to call the runner more than once in a sequence (necessary for running multiple tests sequentially):

• nonce should not be an outside of scope variable: it's better to call the getter, since we're not using these functions in an intense manner: it will be clearer and less prone to mistakes
• registeredParachains should be reset at the beginning of a new run

[joelamouche]

@shawntabrizi this is a prerequisite for #132

[joelamouche]

@shawntabrizi Please review this when you have the time

[shawntabrizi]

If I remember correctly, I didn't do it this way because this messes with submitting multiple txs in the same block. Here, if nonce is called twice where there is some tx still in queue, the nonce in storage will be returned which is not correct for submitting multiple transactions.

[shawntabrizi]

You should def DM me on Riot if you dont see me review your code in a timely manner. For whatever reason, sometimes these review requests fall of my github notifications.

[joelamouche]

If I remember correctly, I didn't do it this way because this messes with submitting multiple txs in the same block

I see. But in that case we're not doing more than once tx in a block for the setup. I could replace with nonce=-1 as per https://polkadot.js.org/docs/api/cookbook/tx/ if you think it's valuable