revm: Update account storage methods in CacheDB

[ngotchac]

So this PR does 2 things in revm::CachDB:

1. It updates the insert_account_storage so that it doesn't override the underlying account info
2. It adds a new method replace_account_storage to completely replace the account storage

For (1), I don't actually know whether it was intentional to override the account info with the default (empty) value. I don't quite see when this would be useful.

For (2), it would be useful for implementing the StateOverride that's in geth, where there is an option to completely override the storage.

I added tests for both methods.

[rakita]

I added CacheDb as i needed utility for tests and didnt think about implication if it is used by others, but it has changed to something usable as foundry is relaying on it. Both changes make sense.

@onbjerg this shouldn't change anything major, but just wanted to notify you as it can has different side effect.