feat(`cast`, `anvil`): add CLI flag to read an array of labels from a file

### Component

Cast, Anvil

### Describe the feature you would like

The labeling feature is awesome, but managing it directly in `foundry.toml` is not the right place when working with a lot of contracts. An option (in `foundry.toml` directly, or via a CLI arg) to set a filepath as somewhere to read labels from, whether JSON formatted, or maybe CSV, would be great!

It would enable using https://github.com/dawsbot/eth-labels easily for example, without having to import it directly in this repo/at build time. It would enable us to generate such a "labels" file for our own use cases.

This might relate to this issue: https://github.com/foundry-rs/foundry/issues/640

### Additional context

_No response_