[llvm] [NFC] [SPIRV] Add SPIRVCombinerHelper and refactor pre legalizer combiner to use it (PR #162735)

[Matt Arsenault via llvm-commits]

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@@ -0,0 +1,60 @@
+
+//===-- SPIRVCombinerHelper.cpp ---------------------------------*- C++ -*-===//
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arsenm wrote:

```suggestion
//===-- SPIRVCombinerHelper.cpp -------------------------------------------===//
```

https://github.com/llvm/llvm-project/pull/162735