✨ Implement dynamic sizing for SQL and Collection readers

[joocer]

Download an initial chunk of records (say 500), from that estimate how many records will fit in 64Mb and then download that many on subsequent batches.

[joocer]

Do a statistical analysis, from the 500 don't just mean the items, work out the standard deviation and assuming the 500 are representative, calculate how many records fit in 64mb with a 90% probability

[joocer]

we're going to start with a simple average until that's not good enough