Add RawClientWithMacAuth to each client

[guggero]

This allows us to use the underlying RPC methods directly while still taking advantage of the macaroon management.

Using the raw RPC methods directly can be useful when a new method isn't implemented in lndclient yet or when we want to pass the raw RPC request method directly instead of converting it to the lndclient structs.

Pull Request Checklist

• PR is opened against correct version branch.
• Version compatibility matrix in the README and minimal required version
  in lnd_services.go are updated.
• Update macaroon_recipes.go if your PR adds a new method that is called
  differently than the RPC method it invokes.

[bhandras]

LGTM, uTACK 🎉

[ellemouton]

lgtm!