replace generic stateprovider with boxed trait

[mattsse]

this is currently generic over stateprovider

reth/crates/engine/tree/src/tree/memory_overlay.rs

Lines 17 to 18 in d395df2

	/// Historical state provider for state lookups that are not found in in-memory blocks.
	historical: H,

but only useful if useful if the generic is state provider:

reth/crates/engine/tree/src/tree/mod.rs

Line 670 in d395df2

) -> ProviderResult<MemoryOverlayStateProvider<Box<dyn StateProvider>>> {

since our state_by_hash functions return Box<dyn StateProvider> anyway

we can simplify generics here and simply use Box