Includes:
- Shift to use of spirv-header extinst.nonsemantic.shader grammar.json
- Remove extinst.nonsemantic.vulkan.debuginfo.100.grammar.json
- Enable all optimizations for Shader.DebugInfo

Also fixes scalar replacement to only insert DebugValue after all
OpVariables. This is not necessary for OpenCL.DebugInfo, but it is
for Shader.DebugInfo.

Likewise, fixes Private-to-Local to insert DebugDeclare after all
OpVariables.

Also fixes inlining to handle FunctionDefinition which can show up
after first block if early return processing happens.

Co-authored-by: baldurk <baldurk@baldurk.org>