[clang] [clang][SPIRV] Add builtin for OpGenericCastToPtrExplicit and its SPIR-V friendly binding (PR #137805)

[Farzon Lotfi via cfe-commits]

farzonl wrote:

@Naghasan @VyacheslavLevytskyy there is an issue in SemaSPIRV.cpp

```
clang/lib/Sema/SemaSPIRV.cpp:132:3: error: default label in switch which covers all enumeration values [-Werror,-Wcovered-switch-default]
  132 |   default:
      |   ^
1 error generated.
```

https://github.com/llvm/llvm-project/pull/137805