Harden against finalized block spam

[michaelsproul]

Proposed Changes

• Remove a double block root calculation for blocks that are prior to finalization based on their slot. We just plumb the error through from block_verification.rs. This has the potential to halve the time spent rejecting these messages (from 10-20ms to 5-10ms).
• Increase the peer penalty for blocks that are prior to finalization. They are still Ignored though rather than rejected, as that's what the spec requires.
• Increase the peer penalty for blocks that conflict with finalization (side chains that are obsoleted by finalization). They are now Rejected, which also aligns with the spec.

Additional Info

• Remove check_block_against_anchor_slot. I added it in 2021 when I implemented checkpoint sync, but it's superfluous because the anchor slot is always <= the finalized slot, so any block caught by the anchor check will be caught by the finalized slot check.
• There are a few other places we could plumb through the block root: BlockIsAlreadyKnown, RepeatProposal, NotFinalizedDescendant, BlockIsNotLaterThanParent, TooManySkippedSlots are all prior to the proposer signature check.

[michaelsproul]

Note to self after recent discussions: if we allow checkpoint sync from a state newer than finalized, then we do need the separate anchor slot check 🤔