Add support for DXBC SM4 output

[flibitijibibo]

Definitely a large project so it would need a big motivator... but it's within our reach:

Existing implementation in 9on12:

• Converter
• Runtime (includes linker)

Signing can be done with DxbcSigner which is redistributable.

The main benefit is removing the dependency on an HLSL compiler, which should be faster in general and also open up the door to dxvk-native 11 support.

• [ ] New bytecode4 emitter
• [ ] Separate hlsl and bytecode4 paths in mojoshader_d3d11