Don't attempt to read password on stdin if stdin isn't a tty

[mrmr1993]

Checklist:

• Document code purpose, how to use it
  • Mention expected invariants, implicit constraints
• Tests were added for the new behavior
  • Document test purpose, significance of failures
  • Test names should reflect their purpose
• All tests pass (CI will check this if you didn't)
• Serialized types are in stable-versioned modules
• Does this close issues? List them:

Closes #6681

[nholland94]

Even if stdin is a tty, I think we still might want to just skip this prompt. I believe @lk86 was saying that this prompt gets hidden from users by other logs and that users end up not seeing the prompt. I'll defer to @lk86 to confirm what we should/shouldn't do.

[lk86]

We're always instructing people to either use an environment variable or -block-producer-password, so if we don't have a password it should always fail and point people to CODA_PRIVKEY_PASS + -block-producer-password.

[mrmr1993]

Updated. I've added a new function that only checks the environment variable, and changed the calls from the daemon command's startup to go through that.

The client/accounts/etc. commands that require a password will still prompt if needed, and I don't this this causes us the same issues, so leaving the old functionality available to be used there.