Benchmark Demo: Default asset triangle counts are too far off the indicated amount

Triangle counts in the meshes vary too much from the numbers indicated in UI. Make them match more closely.

Currently the triangle counts are:

• 1k model: 3 x 336 triangles (=1008)
• 10k model: 1 x 21196 + 4 x 3792 triangles (=36364)
• 50k model: 1 x 81734 + 4 x 1600 triangles (=88134)
• 100k model: 1 x 154397 + 4 x 1600 triangles (=160797)
• 500k model: 1 x 879892 + 4 x 1600 triangles (=886292)

1k model is fine, the others need tweaking.