* 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>