Use true bytes not compressed bytes for calculated cost_per_byte in algorithm

[MitchTurner]

The committer isn't aware of the original byte size of each block, just the compressed bytes. We need this information to calculate the real value of cost_per_byte.

We should record the bytes for each block in unrecorded_blocks and use that value when updating the latest_cost_per_byte and ensure that is the case for any place we are using the block bytes.