Develop a more in-depth integration test for the TS rpc client

[geoknee]

Currently, we spin up a number of rpc servers, and use the client-runner ts-node script to drive them.

A better solution would be to write a jest test to replace the ts-node script.

It should follow https://github.com/statechannels/go-nitro/blob/e8451e1a633a490056dbb9d2b047a32f263ec75a/node_test/rpc_test.go in terms of what it looks to cover.

It should be kept separate from unit tests (i.e. a separate script in the package manifest, possibly a separate jest config)

It may want to pull in some of the isServerUp helpers from the client runner.