cmd/{geth,utils}: read genesis block from db in chain import

[gballet]

I discovered that importing blocks from a non "official" chain is broken.

This is because the import function will call MakeGenesis, which doesn't try to load any block from the db, and falls back on the hardcoded ones. If none of these hardcoded genesis blocks work, it YOLOs it by returning a nil genesis. This doesn't go well: at some point, the genesis is filled with default values, whose hash never matches that of the genesis block that was stored with geth init.

Somehow, the genesis block should be passed to MakeChain. So this PR introduces MakeChainWithGenesisBlockAndChain so that this info can be recovered from the DB.

I'm not a big fan of it, and I think we should remove MakeChain altogether. But I'm putting this out there to gather input on the approach, which is perfectible imo.

Ultimately, this is coming down to SetupGenesisWithOverrides doing too much, that should be refactored. Happy to have the discussion here.

[holiman]

Do you have an example genesis + chain to repro / test with?

[gballet]

Do you have an example genesis + chain to repro / test with?

same as in this issue #30878

[gballet]

Probably fixed by #30907, but let's confirm when it's merged.

[MariusVanDerWijden]

@gballet could you confirm that this was fixed by #30907 ?