* eth/catalyst: build the execution payload async
* miner: added comment, added test case
* eth/catalyst: miner: move async block production to miner
* eth/catalyst, miner: support generate seal block async
* miner: rework GetSealingBlockAsync to use a passed channel
* miner: apply rjl's diff
* eth/catalyst: nitpicks
Co-authored-by: Gary Rong <garyrong0905@gmail.com>