[Tooling] How to watch a cabal project

From [this tooling idea](https://github.com/haskellfoundation/tech-proposals/pull/46)

When I am in an abitrary directory, how can I know which files need to be watched for changes?

The use case is that I have developed a way to discover the tests in a `tasty` testsuite, and how to expose them in the VS Code UI.

The way they are discovered is by running the test suite in "discover mode" and subsequently in "run test mode".

I need to re-run discovery of tests for a test suite each time any files in the source code change. Does cabal expose such a functionality?

Fendor linked the following issue a potential fix: https://github.com/haskell/cabal/pull/7500