Use fully qualified names in spec

A problem I routinely have when trying to read the SPIR-V spec is that finding things is a chore as some things have very generic names like `Offset`, `R` or `2D`, etc which have multiple references in the spec.

I think it would be better to use fully qualified names everywhere such as `ImageOperandsOffsetMask`, `ImageChannelOrderR`, `Dim2D`

This is not just a problem for these specific names and enums, this problem appears for a huge amount of names in the SPIR-V specification and makes it really hard to search for things.

The issue names the SPIR-V specification but no file or test. Start by locating the specification’s definitions and references for names such as Offset, R, and 2D, then determine the complete naming scope. Done means generic names are consistently replaced with fully qualified names throughout the specification.

Written by the indexing model from the issue text.