Enable quick start to run with local-sequencer

[MSevey]

To help with different tutorials and guides, it would be useful to be able to run a custom sequencer with the quick start command.

Currently if you try you get an address conflict:

rollkit start --rollkit.aggregator --rollkit.da_address http://localhost:7980
Error intercepting command:  Reading rollkit.toml: no rollkit.toml found
I[2024-11-05|14:40:59.826] Found private validator                      module=main keyFile=/Users/matt/.rollkit/config/priv_validator_key.json stateFile=/Users/matt/.rollkit/data/priv_validator_state.json
I[2024-11-05|14:40:59.826] Found node key                               module=main path=/Users/matt/.rollkit/config/node_key.json
I[2024-11-05|14:40:59.826] Found genesis file                           module=main path=/Users/matt/.rollkit/config/genesis.json
ERROR: failed to launch mock sequencing server: listen tcp 127.0.0.1:50051: bind: address already in use

I think we just need to add logic to check if there is already a sequencer running on the default port like we do with the DA server.