Separate the builtins by stage and input/output as it's arguably less confusiung.

Note: This only separates the table. It would be nice to also separate the documentation so that vertex position links to a different place than fragment position and sample_mask input links to different place than sample_mask output. That change can happen in another PR.

Issue #5081

Note: Other GPU API specs do not combine inputs and outputs from multiple stages into one.

• GLSL sections 7.1.1, 7.1.2, 7.1.3

• HLSL

• MSL sections 5.2.3.1, 5.2.3.3, 5.2.3.4, 5.2.3.5, 5.2.3.6

Result: