Add a testbed project for watchOS

### What is the problem or limitation you are having?

There's not currently any way to (easily) test the operation of watchOS.

### Describe the solution you'd like

The Python patch should be extended to include a testbed project for watchOS.

### Describe alternatives you've considered

None

### Additional context

watchOS projects are quite different to other platforms; however, it may be possible to crib a lot of content from the iOS testbed project.

It may also be worth investigating if a single testbed can be used for all Apple platforms, with multiple targets in a single project.

Start by locating the Python patch and the existing iOS testbed project, then compare how its project and targets are structured. Investigate whether watchOS needs a separate testbed or can share a multi-target Apple project; done means the repository includes an operable watchOS testbed and the project approach is established.

Written by the indexing model from the issue text.