We used a size computation to generate reasonably sized batches, but the
ProtoSize call is fairly expensive as it requires a conversion to a wire
type etc. We don't need that much precision. Instead, just limit to 1000
files or 5000 blocks, which is likely approximately that much data
anyway.
Closes#10707
Signed-off-by: Jakob Borg <jakob@kastelo.net>
ef4629ea56