Improve data flows

[lodejard]

Several places are doing array copies and growing-reallocations which should be an array of arraysegment of pooled byte[]... This relates to primary input/output data flows

[Eilon]

This is a super old bug but it was in the alpha4 milestone, so moving to RC1 to reevaluate.

[Eilon]

@lodejard was this done or not? Just wondering what label to tag it as.