[llvm] [mlir][spirv] Add mlir-spirv-tests CI to run for mlir-spv target tests (PR #152124)

[Jakub Kuderski via llvm-commits]

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@@ -9,6 +9,7 @@ on:
     paths:
       - 'llvm/lib/Target/SPIRV/**'
       - 'llvm/test/CodeGen/SPIRV/**'
+      - 'mlir/test/Target/SPIRV/**'
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kuhar wrote:

Also it's not just Target tests, also the serializer/deserializer implementation

https://github.com/llvm/llvm-project/pull/152124