Performance improvements for WebGL shape drawing

[davepagurek]

Resolves #7237

This makes two changes:

• We no longer create edges on models that don't have any, meaning if you never create strokes, you never have to incur the cost of calculating them.
• Fixes a shape drawing special case: we can draw individual triangles without tessellation, but what should have been an = was an === so it wasn't being applied, oops 😬

I tested with this https://editor.p5js.org/davepagurek/sketches/vmiMgGi5s which makes a new geometry and draws it each frame. The perf I got was:

Chrome

• No stroke changes: 5fps
• Skip strokes: 11fps
• Add triangle check: 12fps

Firefox

• No changes: 4fps
• Skip strokes: 8fps
• Add triangle check: 9fps

I didn't make the other change requested in the issue to make buildGeometry update the line vertex data when you add a new shape. This is because when we add it, we have to transform every vertex anyway. This is probably not less work than just recreating it, and if you do any other operation (e.g. add this geometry into another geometry), you'd be doing more work overall by transforming twice.

PR Checklist

• npm run lint passes
• Inline documentation is included / updated
• Unit tests are included / updated

[perminder-17]

Good catch.

[perminder-17]

This PR also fixes issue: #6318. Thanks;)