not a problem atm, and shouldn't be ever but in theory could be.

currently when prepare proposal creates a block it won't filter based on bytes, only by the square size. this results in producing blocks that are too large and always fail, halting the network when the mempool is full.

to fix this, we should probably just not allow the max block bytes to be lower than the square size or add an additional filter in prepare. the problem with adding an additional filter it needs to be after the existing filtered square. this might be a minor logistical annoyance.

once we fix the mempool, this will actually break the existing evictions test, since a fixed mempool will result in filling the block past the 1MB limit imposed there, and the square size is set to the default which is 256 (32MB)