[llvm] [SampleFDO][TypeProf]Support vtable type profiling for ext-binary and text format (PR #148002)

[Paschalis Mpeis via llvm-commits]

================
@@ -671,7 +761,7 @@ SampleProfileReaderBinary::readProfile(FunctionSamples &FProfile) {
       return EC;
   }
 
-  return sampleprof_error::success;
+  return readCallsiteVTableProf(FProfile);
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paschalis-mpeis wrote:

nit: Maybe it is more idiomatic and extensible to keep `return success`, after reading any additional profiles based on flags?

```cpp
  if (ReadVTableProf)
     return readCallsiteVTableProf(FProfile);
    
return sampleprof_error::success;    
```

(if this recommendation is applied, there's a similar example in `SampleProfWriter`)

https://github.com/llvm/llvm-project/pull/148002