TSL: Add support for rendering to integer-format render targets

[gkjohnson]

Description

Currently it seems to not be possible to render to an integer-buffer render target, which can be useful for all kinds of utilities like picking, occlusion culling, etc. Note this is supported with shader materials and is used in this example, already. This issue is about adding support outputting a uint value:

const target = new RenderTarget( width, height, {
	format: RedFormat,
	type: UnsignedIntType,
} );

const material = new NodeMaterial();
material.outputNode = uint( 10 );

const mesh = new Mesh( geometry, material );

renderer.render( mesh, camera );

Solution

Allow for setting the outputNode to be a uint-type of vector 2, 3, 4, or scalar value, as above. Or a function that returns one of the same types. If outputs can only be of type vec4 in WebGPU then we can require it be

This also implies support for signed & unsigned integer clear colors.

Alternatives

None

Additional context

No response