[txtar] remove unexpected behavior in txtar tests (premines, predeploys)

[zivkovicmilos]

Description

As discussed in #1471, I believe txtar tests should always start with a fresh chain, and not have initial accounts or initial deployments (in genesis). The reason for this being, txtar environments should be heavily controlled by the test maker, and not have unexpected premines and predeploys when the node starts within the test.

Instead, I propose we introduce functionality to control these features, similar to what @deelawn is doing in #1471. This way, the test maker can actually choose to premine or predeploy specific accounts or contracts. It is more explicit, and breaks away from the behavior we have lurking in the codebase of stuff happening behind the scenes without the user's knowledge (especially with chain initialization).

Looking for opinions @moul @gfanton @ajnavarro

[zivkovicmilos]

This was resolved as part of #1471 and #1598

Thank you @deelawn and @gfanton 🙏