feat: getStateDiff / getStateDiffJson decode storage for non local contracts

### Component

Forge

### Describe the feature you would like

We're using foundry to analyze transactions via `getStateDiff[Json]`.

For this case it would be very useful to have state decoding also for touched contracts that are **not** part of the current codebase. Not exactly sure about how it works on tracing, but i guess it would be a matter of downloading the contracts from the explorer when running the tests.

### Additional context

`getStateDiff[Json]` already is a huge improvement to local transaction analysis, but it falls short when using foundry for testing upgrades against forks / interacting with pre-deployed existing contracts.
Therefore it would be great to have the ability (even if with a flag) to have state decoding on external contracts as well.