Spec issue: gpuweb/gpuweb#1354

We can initially develop these tests against the feature name "chromium-experimental-multi-draw-indirect" (available in Chrome Canary behind chrome://flag#enable-unsafe-webgpu) and then graduate them to "multi-draw-indirect" eventually once the spec moves forward.

• Validation tests
  • Extend existing draw tests to cover these calls
  • New validation
• Operation
  • Extend existing draw tests to cover these calls
  • Behavior of the draw count buffer and maxDrawCount
  • Pipelines with texture/sampler binding types: see https://issues.chromium.org/issues/379656378#comment3