Zoom 3: Introduced zoom specific task labels

Does what it says on the tin. This is a very small MR to introduce the zoom-specific task labels. These are primarily useful for debugging performance using the analysis tools.

This MR does not implement the labels everywhere they need to be (runner_main. task splitting operations, task weighting etc.). I'll do this as it comes up. I wanted this to focus on getting comments on their introduction and naming.