feat(database): add storage getter to BundleState

[mattsse]

Adds a storage() convenience method to BundleState that retrieves a storage value by address and key.

This mirrors the pattern in reth's ExecutionOutcome where account(), storage(), and bytecode() methods exist for convenient state access.

pub fn storage(&self, address: &Address, storage_key: StorageKey) -> Option<StorageValue> {
    self.account(address)
        .and_then(|account| account.storage_slot(storage_key))
}

[codspeed-hq]

Merging this PR will not alter performance

✅ 173 untouched benchmarks

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_{Comparing mattsse:matt/bundle-state-storage-getter (e578b01) with main (ecd3fc5)}