This PR adds `genesis_gas_limit` parameter within `network_params.yaml`
to make the parameter configurable using Kurtosis.

It seems like
[ethereum-genesis-generator](https://github.com/ethpandaops/ethereum-genesis-generator),
which is being used in this package already has the capability to change
`genesis_gas_limit` by changing `export
GENESIS_GASLIMIT="${GENESIS_GASLIMIT:-30000000}"` within
[defaults.env](https://github.com/ethpandaops/ethereum-genesis-generator/blob/master/defaults/defaults.env#L27).
This feature didn't seem like it was directly transferred to the
`ehtereum-package`.

Tested locally with the `main` branch and changing the
`genesis_gas_limit` value to `50000000`.
![Screenshot from 2024-07-26
11-26-12](https://github.com/user-attachments/assets/c3ad1dd9-edd6-461c-bb81-a79de1593833)

---------
Signed-off-by: Ji Hwan <jkim@polygon.technology>
Co-authored-by: Barnabas Busa <busa.barnabas@gmail.com>