The pipeline option was structurally permitted and designed for, but
was never implemented. With the availability of Metal 3, which provides
significant additional bindless argument buffer support, this option is
being removed, in favor of future code enhancements that build on Metal 3.

- Base all argument buffer support around descriptor sets.
- Rename internal functions that test for support for argument buffers.
- Update code documentation accordingly.

- Add MVKPhysicalDeviceMetalFeatures::needsArgumentBufferEncoders to indicate if
  Metal argument buffer encoders are needed to populate argument buffer content.
- Update MVK_PRIVATE_API_VERSION to 38.
- Add MVKArgumentBufferEncoder to handle populating Metal argument buffers
  with or without Metal argument encoders, and pass this to descriptors.
- Indicate support for argument buffers on iOS, when Metal 3 is available.
- MVKConfiguration::useMetalArgumentBuffers set to
  MVK_CONFIG_USE_METAL_ARGUMENT_BUFFERS_ALWAYS by default,
  which means Metal argument buffers are now used by default.
- runcts script enables argument buffers by default.

…rSets().

- Combine MVKMTLArgumentEncoder and MVKArgumentBufferEncoder into
  MVKMetalArgumentBuffer, which holds an arg buffer and its encoder,
  removing need to lock the encoder.
- MVKDescriptorSet tracks argument buffer, and calls to vkUpdateDescriptorSets()
  directly insert resources into the argument buffer.
- Add MVKDescriptor encodeResourceUsage() to encode indirect resource usage
  when using argument buffers.

- Include descriptor element count when calculating
  Metal3 argument buffer encoded size.
- Support MVKPhysicalDeviceMetalFeatures::nativeTextureAtomics
  in argument buffer operations.
- Add ability to log descriptor set layout.
- Support debug logging alongside other logging levels.

- Update SPIRV-Cross version to include latest argument buffer fixes.
- Disable CompilerMSL::Options::force_active_argument_buffer_resources.

- Track OpArrayLength buffer-sizes buffer as an auxiliary buffer in each
  descriptor set argument buffer, as this is how SPIRV-Cross expects it.

- Revert MVKConfiguration::useMetalArgumentBuffers and env var
  MVK_CONFIG_USE_METAL_ARGUMENT_BUFFERS to boolean value, because
  descriptor indexing value is not longer required.
- Update max number of buffer and textures per stage to 1M.

- Refactor and simplify calculating argument buffer resource indexes
	- Remove MVKShaderStageResourceBinding::resourceIndex,
	  and track resource index incrementing locally.
	- Update MVKDescriptorSetLayout::_descriptorCount & _mtlResourceCount
  	  from within MVKDescriptorSetLayoutBinding.

- Refactor and simplify tracking argument buffer usage
	- Rename MVKDeviceTrackingMixin::isUsingDescriptorSetMetalArgumentBuffers()
	  to isUsingMetalArgumentBuffers(), and allow it to be overridden in
	  MVKDescriptorSetLayout.
	- Move and rename MVKDevice::_isUsingDescriptorSetMetalArgumentBuffers
	  to MVKPhysicalDevice::_isUsingMetalArgumentBuffers.
	- Remove MVKPhysicalDevice::supportsDescriptorSetMetalArgumentBuffers();
	- Remove MVKDescriptorSetLayout::isUsingMetalArgumentBuffer() and replace
	  with overridden isUsingMetalArgumentBuffers() function.
	- Rename MVKDescriptorSet::isUsingMetalArgumentBuffer to hasMetalArgumentBuffer().
	- Remove MVKDescriptorSetLayoutBinding::isUsingMetalArgumentBuffer().
	- Remove MVKDescriptorSetLayout::isPushDescriptorLayout().

- Update debugging logging
	- Refactor and enhance ability to log descriptor set descriptions for debugging.
	- MVKPipelineLayout support debug logging and remove a few unused member functions.
	- Adjust whitespace in logging of instances and devices.

- Update MVK_PRIVATE_API_VERSION to version 43.