[Mining] always, always, always send a signed Nakamoto block to _all_ signers, and have the signers eagerly process them.

[jcnelson]

Block production can only happen as fast as the 30th percentile signer can confirm all of the next block's parents, so the miner is going to need to do a thorough job pushing signed blocks to all signers. I think this can happen via StackerDB, in addition to the block-push mechanism:

• The miner simply stores its last-signed block in StackerDB as well as its proposed block
• The signer verifies that the last-signed block in the miner's StackerDB record has been processed, and if not, it eagerly does so

The reason I'm recommending this additional step is because the .miners contract offers targeted block delivery to signers, whereas block-push is just a one-shot best-effort transmission means.