Unable to specify coverage reports flags per file

Current way to define flags forces them to apply to all files part of a single upload step. Ideally the flags should be per file and not per upload action.

This makes Github Actions definition much harder to manage as we are forced to add extra calls to the upload action, especially as GHA does not have any support for looping.

It would be far more flexible if we could so something like:

    - name: Upload coverage to Codecov
      uses: codecov/codecov-action@v4
      with:
        directory: ./coverage/reports/
        files: ./coverage1.xml:unit,./coverage2.xml:e2e,!./cache # <- note the `:flag` after file pattern.
        # flags: unit,e2e

Or maybe someone else has another idea?