feat: allow to configure block and batch frequency

[tomyrd]

One of the ways we found to speed up the integration tests in the client was to increase the frequency of blocks in the instantiated local node. We had to add a command to edit these values but we could have a better way via a config file or env vars.

see if we could add a way to configure this with env vars or something similar?

Originally posted by @igamigo in 0xMiden/miden-client#763 (comment)

[Mirko-von-Leipzig]

This will be easy as a follow-up item after #732 as then we can simply add configuration args for them with the current constants as the default value.

[bobbinth]

Should we add this to v0.8 milestone?