Switch `--chain=dev` to PoS and remove Clique

[yperbasis]

We can use @taratorio's mock CL.

Once done, we can remove StageHeaders & StageBodies and also the PoW mining loop.

[VBulikov]

yperbasis added Imp1 as Importance

[VBulikov]

VBulikov changed Importance from Imp1 to Imp2

[AndreaLanfranchi]

If I may ... please don't. This is one feature that maintains KISS principle (for end users of course). :)

[taratorio]

If I may ... please don't. This is one feature that maintains KISS principle (for end users of course). :)

@AndreaLanfranchi this task is not about dropping support for --chain=dev - it is more of an internal simplification for us and it intends to preserve support for it.

[AndreaLanfranchi]

Thank you ... this is important clarification.
Nevertheless (no arguing intended) I believe PoW + clique could still be an incredibly powerful setup for quick private chains removing all the complexities of PoS. Just my two cents.
Glad in the end --chain=dev can still be a thing.

[yperbasis]

cmd/devnet was sunset in PR #16882

[yperbasis]

TODO: remove https://github.com/erigontech/erigon/blob/main/docs/DEV_CHAIN.md

[yperbasis]

PoW mining removed in #17813