Big state hashTreeRoot() time in lodestar

[twoeths]

Problem description

state hashTreeRoot() takes up to 1s - 1.5s frequently, need to find a way to improve it

this is likely to happen after processing an epoch, in rare case it could be up to 1.8s on holesky #6194

Solution description

Reduce it as much as possible

• Improve our hash function either by SIMD here or (most likely) hashtree work by @wemeetagain
• Find a way to consume it in persistent-merkle-tree

Additional context

No response