Add `[anvil]` section to `foundry.toml`

### Component

Anvil

### Describe the feature you would like

I have forking configs in hardhat.config.ts, it changes according to the following env variables:

- NETWORK
- FORK
- FORK_BLOCK_NUMBER
...

sometimes anvil node is better so I'd like to use anvil for running forkmainnet, in this case how can I let anvil read directly those configs instead of putting complex input parameters such as --fork-url etc.

### Additional context

_No response_