Having the grpc bindings in the pyln-testing package was always a bit
strange, however it came with additional issues. Due to the way that
protos are handled by protobuf, any name clash, independently of where
we import the protos, would cause an import error. This usually
happens in diamond-pattern dependencies, and so pull out the generated
files into their own package that everyone else can rely on.
Changelog-None
This allows us to re-use existing tests (assuming the call and fields
are covered by `cln-rpc` and `cln-grpc`) to test the full roundtrip
from test over the grpc interface to the json-rpc interface and back
again.
You can switch to the grpc interface by setting the `CLN_TEST_GRPC`
environment variable to 1, but for now only very few shims are
implemented (due to the non-generated nature of LightningRpc).
