test: adds setup for mock-service-worker

[schottra]

This is the first step in using mock-service-worker to mock our data instead of the messy mocking at the apiContext or axios level.

The basic idea is that we have a set of mock objects defined in src/mocks and a set of handler functions for each of the endpoints we use (there are only a handful). There will be a default set of objects that are loaded into the mock server for simple uses cases. Specific cases can add additional single-test handlers via mockServer.use. I decorated the mock server object with insert* functions for adding handlers for a specific entity type, to reduce the clutter in tests.

This PR just gets mock-service-worker integrated with a few simple objects and fixes whatever broke in doing so (mostly around some tests of the AdminEntity code).

A note:
Going forward, we will not test things like whether the correct query params were passed to an API call. We will test what happens in the failure cases. If we really need to test a specific behavior on query params, MSW can be set up to handle the query params and return different data. And then we can allow the component to render the data in the special case and assert that it looks the way we expect

Change list

• Added mock-service-worker
• Updated the way our env variables are read to remove the unnecessary isServer() check. We can prefer process.env if it exists and otherwise try window.env.
• Added handlers for WorkflowExecution, NodeExecution, Workflow and Project.
  • Note: Handlers all use a shared response function which will encode the response to protobuf and set the correct headers, since the client code in AdminEntity will expect that and attempt to decode it. This is about as realistic a response as we can get.
• Added one mock object for a WF Execution and a small list of sample projects.
• Added code to import and create handlers for the default data objects
• Updated and/or removed some tests which were attempting to mock AdmintEntity. We will let them call all the way through to axios and operate data returned from our mock server.
• Updated some import statements of AdminEntity to be more specific, since the index-type includes cause circular reference issues.
• Moved around some constants for api path generation to make sure that the mock server and client code calling it will use the same prefix.
• Added some temporary empty tests to make Jest happy until I refactor the suites in question in my next PR.
• Upgraded typescript to fix error with types from msw, jest, ts-jest, and babel-jest to versions which support TS 4+. Fixed minors issues resulting from the upgrade.

[BobNisco]

Are these intentionally kept in?

[schottra]

Yep. This keeps the test runner from throwing errors. I will remove them in the next PR when I fix and re-enable the commented-out tests.