Allow raw RPC calls via cargo contract rpc

[cmichi]

cargo contract rpc [options] METHOD [PARAMS]

Users cannot make raw RPC calls to the node with the currently available commands.

Adding this capability would improve the debugging process by giving developers direct access to the node's RPC interface, making it easier to diagnose, fix, and experiment with different scenarios.

[SkymanOne]

This looks like we need to copy the API from https://github.com/paritytech/ink/blob/master/crates/e2e/src/subxt_client.rs perhaps we can move the implementation there and then import it in ink_e2e crate.

I also makes sense for #1213 to get merged first.