Increasing Share Size

[evan-forbes]

We should discuss the trade-offs of increasing the share size. While this was done in other synchronous settings, we have only recorded it in #724 afaik.

repeating some info from #724 and stating the obvious:

• we'd have to increase the share reserved bytes to 2 for contiguous shares
• our max block size would double to 8MB assuming we don't change the max square size
• it would also double the amount of data that light clients have to download from sampling
• size of the DAH stays the same

Ideally, we would start with a share size and keep it for the life of the chain, but since we will likely want to change it in the future, we also want to consider what it would look like to increase the share size via a hardfork.

Most importantly, we also want to experiment with how, increasing the share size would affect DAS. If it does, what would be the ideal size?