BM-1765: mine by default, opt out with env

[austinabell]

Passby also reduces the default mining job size to ~1h on 5090, I've found that when consistently participating in the market, 4h is too long where it would be inconsistent where it is included in the epoch. This is an updated guess of what the default could/should be.

• Updates just broker to just prover (broker was already overloaded given it started bento also)
• Removes just mine command and rolls it into just prover
  • BOUNDLESS_MINING=false to disable the mining process
• Adjusts default mining job size as mentioned above