Integrate DXC for translating HLSL for use in DX12. This will work
around FXC limitations and unlock the use of more advanced HLSL features
such as subgroups.
This hardcodes the use of DXIL, but it could be adapted (with a bit of
effort) to choose between DXIL and HLSL at runtime.
The MSL translation of the prefix example had its bindings permuted; a
flag prevents this (but, as is typical for shader translation,
potentially creates other problems).
Also use explicit unsigned literal to avoid DXC warnings.
Add a clear stage and associated tests, and also use it on non-Vulkan
backends to clear the state buffer.
While that's a workaround and will go away when we implement the actual
clear command, it's also a nice demo of how the new "stage" structure
composes.
Use an array of bindtypes rather than the previous situation, which was
a choice of buffer counts, or a heavier builder pattern.
The main thing this unlocks is distinguishing between readonly and
read/write buffers, which is important for DX12.
This is WIP, the Metal part hasn't been done, and the old stuff not
deleted.
Part of #125
This adds a prefix sum test. This patch is also trying to get a little
more serious about structuring both the test runner (toward the goal of
collecting proper statistics) and pipeline stages for the tests.
Still WIP but giving good results.
