Understand the hardware requirements for simple nightshade block producers

[bowenwang1996]

When we transition from one shard to eight shards in simple nightshade, block producers need to track all shards. As a result, they may need to have better hardware (more cpus more example) than what is currently specified in the docs. After #3825 is done, we should run some experiments to understand what changes to hardware are needed for block producers. We could then potentially batch this change in hardware requirements with #4461 to update the fees.

[bowenwang1996]

To be more specific, we need:

• A cluster with 100 nodes running and loadtest it with transactions. For this part we can take/modify the existing mocknet scripts
• We also need to change the genesis configuration to make sure that every validator tracks all 8 shards. This can be done by modifying num_block_producer_seats_per_shard.

cc @nikurt