Add support for SPV_KHR_non_semantic_info
This entails a couple of changes:
- Allowing unknown OpExtInstImport that begin with the prefix `NonSemantic.`
- Allowing OpExtInst that reference any of those sets to contain unknown
ext inst instruction numbers, and assume the format is always a series of IDs
as guaranteed by the extension.
- Allowing those OpExtInst to appear in the types/variables/constants section.
- Not stripping OpString in the --strip-debug pass, since it may be referenced
by these non-semantic OpExtInsts.
- Stripping them instead in the --strip-reflect pass.
* Add adjacency validation of non-semantic OpExtInst
- We validate and test that OpExtInst cannot appear before or between
OpPhi instructions, or before/between OpFunctionParameter
instructions.
* Change non-semantic extinst type to single value
* Add helper function spvExtInstIsNonSemantic() which will check if the extinst
set is non-semantic or not, either the unknown generic value or any future
recognised non-semantic set.
* Add test of a complex non-semantic extinst
* Use DefUseManager in StripDebugInfoPass to strip some OpStrings
* Any OpString used by a non-semantic instruction cannot be stripped, all others
can so we search for uses to see if each string can be removed.
* We only do this if the non-semantic debug info extension is enabled, otherwise
all strings can be trivially removed.
* Silence -Winconsistent-missing-override in protobufs
