docs(anvil): document parameter each custom RPC method expects

[AbhinavMir]

Component

Anvil

Describe the feature you would like

Currently the anvil reference only points out the available RPC methods, and while for generic RPC methods (eth_*), we have docs on the expected parameters (ref.), this isn't the case for other rpc methods (anvil_* etc.) and I couldn't find them on HH's docs either. Would be great if they were written in one place on the reference!

cheers

Additional context

No response