THRIFT-5811: Add ESM support to nodejs codegen

Client: nodejs
Patch: Cameron Martin <cameronm@graphcore.ai>

This closes #3083

This adds a flag to the JS generator to output ES modules instead of CommonJS. This is only valid when targeting node. A lot of the changes here are to test this.

The `testAll.sh` script now generates an ES module version of the services and types, and tests the client and the server with these. This has a few knock-on effects. Firstly, any module that imports a generated ES module must itself be an ES module, since CommonJS modules cannot import ES modules. ES modules also do not support `NODE_PATH`, so instead the tests directory is converted into a node package with a `file:` dependency on the root thrift package.