perf(state): avoid full header decode in StateAtBlockNumber

[ongyimeng]

StateAtBlockNumber currently calls pruner.HeaderByNumberIfStateRetained, which fully decodes the block header even though opening historical state only needs:

GlobalStateRoot
Hash, for the state-retention hash → number check

A partial-header decode could avoid materializing heavier unused fields such as EventsBloom.

Use #3782 as reference implementation

[0xsamalt]

Hi @ongyimeng, I'd like to work on this one, will follow #3782 as the reference implementation.