Do not use `Option` to wrap `GenesisConfig` fields (#8275)

Currently we wrap every `GenesisConfig` field in an `Option`, while
we require `Default` being implemented for all pallet genesisconfigs.
Passing `None` also results in the genesis not being initialized, which
is a bug as seen from the perspective of a pallet developer?

This pr changes the fields of the `GenesisConfig` to non `Option` types.