Add integration tests against ic-ref

[gobengo]

It should test everything that is historically been in sdk's ./e2e/node. But @hansl told me that's only two tests so far.
https://github.com/dfinity-lab/sdk/tree/master/e2e/node

[hansl]

Also, reproducing the test suite from the ic-ref repo, like we are doing for rust-agent (you can look at the ref-tests crate in rust agent).