[FR]: custom tsconfig targets for different generated ts_project types

### What is the current behavior?

All `ts_project` targets use the same logic to find the tsconfig.

### Describe the feature

The generated `ts_project` for tests (or custom targets) might want different tsconfig files. Maybe change `js_tsconfig filename.json` to `js_tsconfig [target_group] filename.json` to support overriding the default config per source group...