WebGPU support for int and uint vertex attributes

[mvaligursky]

Shaders are now processed for WebGPU not only to handle uniform buffers, but additionally to handle different vertex formats. Specifically - till now only float based attributes were supported, but this PR adds support for int and uint attributes.

Shader attribute declaration like this:

attribute vec4 vertex_position;

gets translated to this format, if the vertex format specifies position as TYPE_INT32 for example:

attribute ivec4 _vertex_position;
vec4 vertex_position = vec4(_vertex_position);

• additionally, removed some manual workaround to handle this specifically for the skinning.
• also, uniform arrays of 1 are handled now correctly - before they were assumed to not be arrays, so this now works:
  uniform float data[1]

This makes our bitmoji characters work, as they provide positions in int16 format.
(Note that there is still some morphing issue with them, for a separate PR)

skinning.mov

[slimbuck]

approving with a few tiny comments