Streams with many interior deletes was causing issues due to the fact that the interior deletes were represented as a sorted []uint64.
This approach introduces 3 sub types of delete blocks, avl bitmask tree, a run length encoding, and the legacy format above.
We also take into account large interior deletes such that on receiving a snapshot we can skip things we already know about.
Signed-off-by: Derek Collison <derek@nats.io>
* If we don't encode the `size`, it is lost during an encoding-decoding round-trip
* If we don't check capacity, we might reallocate needlessly instead of just growing the slice
Signed-off-by: Derek Collison <derek@nats.io>
