Add typography benchmark tests for textToContours()

[LalitNarayanYadav]

Resolves #8968

Changes:

• Adds textToContours() benchmarks to test/bench/typography.bench.js, continuing Add typography performance tests #8918
• TO_CONTOURS_CASES is derived from TO_POINTS_CASES, so the strings, text sizes and sampleFactor are identical across the textTo___ benchmarks
• Adds a drawContours() helper for the render: true case
• Adds the contours suite to the 2D, WebGL and WebGPU describe blocks
• Asserts the total point count across contours matches the existing textToPoints() expectations (same sampleFactor: 0.5, same variance)
• Verified with npx vitest bench --run test/bench/typography.bench.js --project unit-tests-webgpu -t "textToContours", which passes for 2D, WebGL and WebGPU

Note: the render case is about 10x slower than the non-render case in WebGL and WebGPU, because drawContours() calls beginShape/endShape once per contour.

cc @shakeelmohamed for review.

Screenshots of the change:
N/A (benchmark tests only)

PR Checklist

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