Separate Tracks for Components and Phases (#31525)

Previously we were showing Components inside each lane track but that
meant that as soon as you expanded a lane you couldn't see the other
line so you couldn't get an overview over how well things were
scheduled.

This instead moves all the Components into a single top-level track and
renames the previous one to a "Scheduler" track group.

<img width="1352" alt="Screenshot 2024-11-12 at 8 26 05 PM"
src="https://github.com/user-attachments/assets/590bc6d3-3540-4ee4-b474-5d733b8d8d8d">

That way you can get an overview over what React is working on first and
then right below see which Component is being worked on.

Ideally the "Scheduler" track would be always expanded since each Track
is always just a single row. Now you have to expand each lane to see the
labels but then you're wasting a lot of vertical real estate. There's
currently no option to create this with the Chrome performance.measure
extensions.

<img width="1277" alt="Screenshot 2024-11-12 at 8 26 16 PM"
src="https://github.com/user-attachments/assets/4fc39e35-10ec-4452-ad32-c1c2e6b5e1a8">