- Correctly populate the field `currentFileId` with the presence of include directive
- Support lazy OpLine/OpDebugLine generation only when a real instruction is added instead of a debug location is set
- Improve the debug location tracking to per-block instead of just per-builder
- A few bug fixes related to debug source info
1. Pull OpDebugFunction, OpDebugScope and OpDebugVariable for params out
of makeFunctionEntry.
2. Put above in a separate function called setupDebugFunctionEntry,
which also accept line number and set it correctly in builder.
3. Call setupDebugFunctionEntry in makeFunction. Also special case
handle entry function since it's created ealier elsewhere.
Currently no debug info is emitted for buffer reference types, which
resulted in the SPIR-V backend code asserting when trying to emit the
debug info for struct member that had such a type. Instead, the code now
skips such struct members. Full debug info for buffer references may
require forward references in the debug info instructions, which is
currently prohibited by the spec.
