Improve shader attribute semantic inferrence and allow user to specify/override

[ben-clayton]

GAPIS currently uses name pattern matching to find the 'position' stream.
It would seem that Unreal obfuscates their shader code, including the vertex attribute names:

0: in_ATTRIBUTE2, XYZW_U8_NORM
1: in_ATTRIBUTE15, XY_F16
2: in_ATTRIBUTE4, XYZW_F16
3: in_ATTRIBUTE0, XYZ_F32
4: in_ATTRIBUTE1, XYZW_U8_NORM

• We could get GAPIS to fallback to looking for XYZ_F32 streams for position, but that's quite a risky solution.

• I still like the idea of analyzing the shader to infer the attributes that contributed to gl_Position, but that's a fair amount of work.

• We should just let the user pick the streams they want to visualize, with some sort of sensible defaults.

[dsrbecky]

B is not entirely insane if we use SPIR-V

[ben-clayton]

I've tried a few Unreal titles now which seem to mostly work. Removing from milestone.