Upgrade earcut to v2.2.4

[mourner]

Upgrade Earcut (library responsible for triangulating polygons) to v2.2.4, bringing performance improvements (up to ~15%) and a fix for a race condition that could cause an infinite loop.

Should improve tile loading times on low zoom levels, particularly the globe view, because half of the worker time is spent triangulating complex water body polygons (50% in earcut before the PR, 40% after).

• briefly describe the changes in this PR
• manually test the debug page
• apply changelog label ('bug', 'feature', 'docs', etc) or use the label 'skip changelog'
• add an entry inside this element for inclusion in the mapbox-gl-js changelog: <changelog>Improve tile loading performance on low zoom levels</changelog>

[karimnaaji]

👍 Looked at the changes from earcut, they look good to me.