Merge #2948

2948: Remove typed command wrappers r=msiglreith,grovesNL a=kvark

Here comes another midnight PR. If you ever looked for a way to make users stick to the last published version (hal-0.3 in our case), look no more. This PR removes a layer from HAL and reorders the exported types so that everyone is guaranteed to have fun fixing their programs. Seriously though, the old way of type re-exports was very inconsistent and messy, both on the HAL and using sides.

To clarify, I think having `Capability`-based wrappers is very useful, it's a great thing to have. Problems are: 1) it's not needed by the backends, and 2) it's not *universally* useful, i.e. things like Rendy, WebRender, and WebGPU can't really take full advantage of it. Therefore, our recommendation is to consider [rendy-command](https://crates.io/crates/rendy-command) as a replacement. cc @omni-viral 

With the removal of typed layers, our names became more solid, and the semantics of clear values is much simpler now.

Fixes #2862
PR checklist:
- [x] `make` succeeds (on *nix)
- [x] `make reftests` succeeds
- [x] tested examples with the following backends: all
- [x] `rustfmt` run on changed code

@grovesNL @msiglreith this PR should probably not hang around for too long, since it's hard to rebase. Only HAL parts needs reviewing, everything else is not as important.

Co-authored-by: Dzmitry Malyshau <kvarkus@gmail.com>
Co-authored-by: Dzmitry Malyshau <dmalyshau@mozilla.com>

examples/compute/main.rs

@@ -8,7 +8,6 @@
  allow(dead_code, unused_extern_crates, unused_imports)
 )]
 
-extern crate env_logger;
 #[cfg(feature = "dx11")]
 extern crate gfx_backend_dx11 as back;
 #[cfg(feature = "dx12")]
@@ -21,10 +20,7 @@ extern crate gfx_hal as hal;
 
 use std::str::FromStr;
 
-use hal::{buffer, command, memory, pool, pso};
-use hal::{Backend, Compute, DescriptorPool, Device, Instance, PhysicalDevice, QueueFamily};
-
-extern crate glsl_to_spirv;
+use hal::{adapter::MemoryType, buffer, command, memory, pool, prelude::*, pso};
 
 use std::fs;
 
@@ -55,16 +51,28 @@ fn main() {
  .find(|a| {
  a.queue_families
  .iter()
- .any(|family| family.supports_compute())
+ .any(|family| family.queue_type().supports_compute())
  })
  .expect("Failed to find a GPU with compute support!");
 
  let memory_properties = adapter.physical_device.memory_properties();
- let (device, mut queue_group) = adapter.open_with::<_, Compute>(1, |_family| true).unwrap();
+ let family = adapter
+ .queue_families
+ .iter()
+ .find(|family| family.queue_type().supports_compute())
+ .unwrap();
+ let mut gpu = unsafe {
+ adapter
+ .physical_device
+ .open(&[(family, &[1.0])], hal::Features::empty())
+ .unwrap()
+ };
+ let device = &gpu.device;
+ let queue_group = gpu.queue_groups.first_mut().unwrap();
 
  let glsl = fs::read_to_string("compute/shader/collatz.comp").unwrap();
  let file = glsl_to_spirv::compile(&glsl, glsl_to_spirv::ShaderType::Compute).unwrap();
- let spirv: Vec<u32> = hal::read_spirv(file).unwrap();
+ let spirv: Vec<u32> = pso::read_spirv(file).unwrap();
  let shader = unsafe { device.create_shader_module(&spirv) }.unwrap();
 
  let (pipeline_layout, pipeline, set_layout, mut desc_pool) = {
@@ -155,14 +163,13 @@ fn main() {
  }));
  };
 
- let mut command_pool = unsafe {
- device.create_command_pool_typed(&queue_group, pool::CommandPoolCreateFlags::empty())
- }
- .expect("Can't create command pool");
+ let mut command_pool =
+ unsafe { device.create_command_pool(family.id(), pool::CommandPoolCreateFlags::empty()) }
+ .expect("Can't create command pool");
  let fence = device.create_fence(false).unwrap();
- let mut command_buffer = command_pool.acquire_command_buffer::<command::OneShot>();
+ let mut command_buffer = command_pool.allocate_one(command::Level::Primary);
  unsafe {
- command_buffer.begin();
+ command_buffer.begin_primary(command::CommandBufferFlags::ONE_TIME_SUBMIT);
  command_buffer.copy_buffer(
  &staging_buffer,
  &device_buffer,
@@ -229,7 +236,7 @@ fn main() {
  }
 
  unsafe {
- device.destroy_command_pool(command_pool.into_raw());
+ device.destroy_command_pool(command_pool);
  device.destroy_descriptor_pool(desc_pool);
  device.destroy_descriptor_set_layout(set_layout);
  device.destroy_shader_module(shader);
@@ -243,9 +250,9 @@ fn main() {
  }
 }
 
-unsafe fn create_buffer<B: Backend>(
+unsafe fn create_buffer<B: hal::Backend>(
  device: &B::Device,
- memory_types: &[hal::MemoryType],
+ memory_types: &[MemoryType],
  properties: memory::Properties,
  usage: buffer::Usage,
  stride: u64,