feat: add key gen util and simple fcu validation test with custom alloc

[Rjected]

Adds two utility methods: generate_keys which just generates a set of key pairs, and public_key_to_address, which converts a PublicKey to Address, hiding details about serialization, hashing, and slicing in the implementation.

Adds another FCU test that validates empty blocks on top of a genesis with a custom alloc.

ref #3836

[codecov]

Codecov Report

Merging #3842 (d3060c6) into main (5ad9b32) will increase coverage by 0.29%.
The diff coverage is 100.00%.

Impacted Files	Coverage Δ
crates/primitives/src/lib.rs	100.00% <ø> (ø)
crates/consensus/beacon/src/engine/mod.rs	77.02% <100.00%> (+1.67%)	⬆️
crates/interfaces/src/test_utils/generators.rs	90.85% <100.00%> (+0.05%)	⬆️
crates/primitives/src/transaction/util.rs	100.00% <100.00%> (ø)

... and 30 files with indirect coverage changes

Flag	Coverage Δ
integration-tests	15.55% <12.06%> (-0.02%)	⬇️
unit-tests	64.22% <100.00%> (+0.30%)	⬆️

Flags with carried forward coverage won't be shown. Click here to find out more.

Components	Coverage Δ
reth binary	26.48% <ø> (ø)
blockchain tree	83.02% <ø> (ø)
pipeline	89.60% <ø> (+2.55%)	⬆️
storage (db)	74.26% <ø> (+0.07%)	⬆️
trie	94.65% <ø> (ø)
txpool	46.55% <ø> (+0.56%)	⬆️
networking	77.66% <ø> (+0.11%)	⬆️
rpc	57.93% <ø> (-0.02%)	⬇️
consensus	65.61% <100.00%> (+0.94%)	⬆️
revm	33.73% <ø> (+0.02%)	⬆️
payload builder	6.61% <ø> (ø)
primitives	88.05% <100.00%> (+<0.01%)	⬆️