Setup initial integration tests with LND #505
Description
We already have rudimentary integration tests with CLN that run in CI. It would be great to also run similar integration tests for LND:
a) Run a dockerized LND node in CI
b) Use a Rust library to interact with LND's gRPC interface. The tonic_lnd crate is the obvious contender here, although last I checked it was only compatible with an older LND version, so we'll have to check whether it would still work for current/future releases for our purposes
c) As a first step, replicate the CLN integration test. Essentially: open channel, send payment, check that it was received as expected. Have LND send a payment, check we received it as expected.