Switch shader indexing from float to int

[dsmilkov]

This change is 

[dsmilkov]

Also tested model-builder and ran benchmark (no perf degrade, actually shaders run slightly faster ~2%)

[dsmilkov]

Same PR includes profiling functionality in the console when math.enableDebugMode() is called.

[nsthorat]

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Reviewed 23 of 23 files at r1.
Review status: all files reviewed at latest revision, 2 unresolved discussions, some commit checks failed.

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src/math/math.ts, line 231 at r1 (raw file):

    let start: number;
    if (this.debugMode) {
      start = Date.now();

use performance.now()

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src/math/webgl/gpgpu_context_test.ts, line 48 at r1 (raw file):

    const result = gpgpu.downloadMatrixFromTexture(texture, 1, 1);
    expect(result[0]).toBeCloseTo(1.234);
  });

add the same test here

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Comments from Reviewable

[dsmilkov]

Review status: 21 of 23 files reviewed at latest revision, 2 unresolved discussions, some commit checks pending.

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src/math/math.ts, line 231 at r1 (raw file):

Previously, nsthorat (Nikhil Thorat) wrote…

use performance.now()

Done.

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src/math/webgl/gpgpu_context_test.ts, line 48 at r1 (raw file):

Previously, nsthorat (Nikhil Thorat) wrote…

add the same test here

Done.

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Comments from Reviewable