57590e0a1f
Instead of comparing the blockhash against the emitted_blocks map to see whether the block is part of the emitter's best chain, we reduce the `last_mempool_tip` height to the last agreement height during the polling logic. The benefits of this is we have tighter bounds for avoiding re- emission. Also, it will be easier to replace `emitted_blocks` to a `CheckPoint` (since we no longer rely on map lookup).