spirv-val MeshEXT: false-positive when multiple mesh shaders of varying output mode are present

[Firestar99]

followup of issue #6307

I see you are filtering out any non-mesh shader entry points, so a module with a mesh and fragment shader would now pass validation.
But wouldn't a module with two mesh shaders, one emitting Triangles and another emitting Lines, still fail? Since the output with PrimitiveTriangleIndicesEXT decoration requiring the entry point to have the OutputTrianglesEXT Execution Mode would see the Line entry point not having it, since it has OutputLinesEXT instead?

from discussion in #6313 (comment)

@spencer-lunarg asked me to create a separate issue for this followup