Introduce header revalidation

[mrBliss]

As mentioned in IntersectMBO/cardano-ledger#1785 (comment), the majority of block replay time is spent in C functions doing crypto checks, see the two top of the profiling report:

COST CENTRE   SRC                                               %time  %alloc
verify        src/Cardano/Crypto/VRF/Praos.hs:(388,1)-(397,33)   46.9    0.1
verify        Crypto/PubKey/Ed25519.hs:(107,1)-(114,30)           6.3    0.0

Both are part of validateHeader, which accounts for 63.2% of the time and 11.6% of the allocations.

Note that this is when we're reapplying blocks, so we know these blocks and thus their headers are already valid. While we already distinguish between block body application and reapplication, we don't do the same thing for block header validation.

Header validation consists of three parts:
https://github.com/input-output-hk/ouroboros-network/blob/cfb465726c9d023ad3ab2a3030d847df27787c3d/ouroboros-consensus/src/Ouroboros/Consensus/HeaderValidation.hs#L474-L492

1. validateEnvelope, which is cheap, but could be skipped during header revalidation. Maybe leave it in as a basic sanity check?

2. updateChainDepState, expensive, as Shelley's implementation uses the Prtcl rule, which calls the Overlay rule, which includes pbftVrfChecks (current hotspot) and praosVrfChecks (likely the future hotspot when more decentralised). The Overlay rule also calls the Ocert rule, which does a KES check with verifySignedKES, which is the second verify from the profiling report.

   Both of these checks should not be needed during revalidation. However, the Prtcl rule and its subrules do update some state, i.e., the ChainDepState, so we can't just not call these rules.

   If the ledger provides a version of updateChainDepState (note that this is a function in cardano-ledger-specs, provided exactly to be used for the Shelley implementation of consensus' updateChainDepState function) that skips the VRF and KES checks, we can use that in consensus to speed up header revalidation.

3. headerStatePush, cheapest of all three and required, as it builds up required state. Must be included in revalidation.

Consensus changes:

• Introduce the reupdateChainDepState method in the ConsensusProtocol class, similar to updateChainDepState, but its implementation can assume updateChainDepState has been called before with the same header so it can skip the expensive crypto checks. I'm not sure yet whether it will still return an Except or just the updated ChainDepState.
• Introduce a function called revalidateHeader in Ouroboros.Consensus.HeaderValidation (to be used when reapplying blocks here), which calls validateEnvelope, headerStatePush, and reupdateChainDepState.

[mrBliss]

Closed by #2521.