Better define externally visible shader Storage Classes (OpTypeBool)

tl;dr - It would be nice to have a more consistent knowledge where `OpTypeBool` are allowed

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in `OpTypeBool` it says

> only with non-externally visible shader [Storage Classes](https://registry.khronos.org/SPIR-V/specs/unified1/SPIRV.html#Storage_Class): Workgroup, CrossWorkgroup, Private, Function, Input, and Output.

but other Storage Classes such as `Generic`, `CallableDataKHR`, etc would also be "non-externally visible"

Also it seems that according to `spirv-val` the `BuiltIn` decoration also matters if it is "external", but I can't find that wording anywhere in the spec

Last thing, It also says

> they must only be used with logical addressing operations, not physical

but is that suppose to just mean anything without `OpMemoryModel Logical` as the spec doesn't define any `operations` that are logical, just the model

Start with the OpTypeBool section of the linked SPIR-V specification and compare its Storage Class wording with Generic, CallableDataKHR, and the other cases raised here. Check spirv-val behavior around BuiltIn decorations and compare the logical-addressing statement with OpMemoryModel Logical. Done means the specification clearly defines externally visible cases, BuiltIn implications, and what logical operations means.

Written by the indexing model from the issue text.