Fix or Remove "bulk_pull_blocks"

[rkeene]

The bootstrap request "bulk_pull_blocks" currently only sends a subset of blocks ("info") rather than a complete set; Additionally, it is paginated in a way that requires sorting (min, max).

Currently nothing uses this primitive and so we could remove it, or, alternatively we could fix it.

In favor of fixing it:

• It is very fast

In favor of removing it

• It requires blocks to be sorted by hash value
• After pulling in all blocks, the whole chain must be assembled and each frontier must be validated with the rest of the network

This ticket is a place to collect comments on how this should proceed.

[rkeene]

Let's remove it.

Any calls to this should return empty set with the current semantics.

In a future release when we need a new slot we remove "bulk_pull_blocks" and replace it the new thing.