[SPIRV] Emit DebugFunction/Definition for both wrapper and real functions

[SteveUrquhart]

#6758 unfortunately caused a regression for shaders compiled without -fcgl. This PR extends the original fix and corrects the regression. We now emit DebugFunction and DebugFunctionDefinition pairs for both the wrapper and the main functions, and a DebugEntrypoint that points at the wrapper function. This survives inlining.

[s-perron]

Lots of tests are failing. Try running the spir-v tests: ninja check-clang-codegenspirv.

[SteveUrquhart]

I'm sorry, I have one test left to fix.

[SteveUrquhart]

@s-perron, the current failure in CI seems to be coming from an optimizer pass. I've attached the spvasm if we use fcgl or O0, and we see there are now 2 DebugFunctions, one for the wrapper and one for src.main. debug_info_manager.cpp:117 in the optimizer asserts.
assert(
fn_id_to_dbg_fn_.find(fn_id) == fn_id_to_dbg_fn_.end() &&
"Register DebugFunction for a function that already has DebugFunction");
I appreciate your advice on this.
spirv.debug.opline.end.of.shader.O0.spvasm.txt
spirv.debug.opline.end.of.shader.fcgl.spvasm.txt

[s-perron]

@SteveUrquhart The DebugFunction instructions do not look correct. Both of them have %src_main for their declaration, which is incorrect for two reasons. First they represent different functions, so they should be different. Second, that value should be the result of a DebugFunctionDeclaration, and not the result of the OpFunction.

   %src_main = OpFunction %void None %15
         %10 = OpExtInst %void %1 DebugFunction %8 %5 %6 3 1 %7 %9 FlagIsProtected|FlagIsPrivate 3 %src_main
         %14 = OpExtInst %void %1 DebugFunction %13 %5 %6 3 1 %7 %9 FlagIsProtected|FlagIsPrivate 3 %src_main