Make it possible to change the protocol parameters / change the protocol parameters to speed up sc rollups

The sc_rollup testnet scenario added in #49 typically runs in two hours on mumbainet. This a bit too slow for TeCI.

As per @lthms, the relevant parameters are:

• smart_rollup_challenge_window_in_blocks: on week per default (40_000 blocks).
• smart_rollup_commitment_period_in_blocks: 60 blocks per default. for tests, can lower to 10.
• smart_rollup_timeout_period_in_blocks: can lower to 10-20

Some experimentation will be necessary to find good values.