[INFRA]: Skip third-party CI when only modifying `ignored` project files.

### Is this a duplicate?

- [x] I confirmed there appear to be no [duplicate issues](https://github.com/NVIDIA/cccl/issues) for this request and that I agree to the [Code of Conduct](CODE_OF_CONDUCT.md)

### Overview

Currently, when I modify for example something in `docs`, the optionals (MatX, Pytorch) are built, too, even though these changes are unrelated. We should build them only if relevant parts of CCCL change.

### Details

An initial implementation will run a script to check if any changes don't match these regexes: https://github.com/NVIDIA/cccl/blob/main/ci/project_files_and_dependencies.yaml#L177-L207

If all files are ignored, skip third party tests.

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For bonus points: Add yaml projects for each third party library that:

- declare meaningful dependencies on relevant CCCL projects
- include the third-party build/test/infra scripts as files that belong to the third-party project

Then check the `inspect changes` output to see if those projects are marked dirty.

### Note

This is low priority as those builds are relatively cheap and do not block PR merges.