Update Spector dashboard to express features that are manually tested

### Clear and concise description of the problem

While our emitter are generating a lot of value out of the box, it has never been a goal to be able to generate every single possible scenarios. But, it is a goal for emitters to be flexible enough to allow customization and manual code to enable any scenarios.

In that spirit, this is possible that some Spector tests cannot be passed by an emitter with only generation and nothing else. For instance, C# union types, Python multipart or Rust API key auth. But we want those tests to pass to demonstrate flexibility.

This issue asks a way for emitter to declare to the Spector report that the test has been passed by writing manual code. Default should be to assume the scenario has been solved with purely generated solution. Once emitter has been passing this information, next step is a UI update to visualize the difference between a test from purely generated code, and a test from generated code with some manual code on top.

### Checklist

- [x] Follow our [Code of Conduct](https://github.com/microsoft/typespec/blob/main/CODE_OF_CONDUCT.md)
- [x] Read the [docs](https://typespec.io/docs/).
- [x] Check that there isn't already an issue that request the same feature to avoid creating a duplicate.