[mlir][vector] Support for extracting 1-element vectors in VectorExtractOpConversion (#107549)

This patch adds support for converting `vector.extract` that extract
1-element vectors into LLVM, fixing a crash in such cases.
E.g., `vector.extract %1[0]: vector<1xf32> from vector<2xf32>`. Fix
#61372.

mlir/lib/Conversion/VectorToLLVM/ConvertVectorToLLVM.cpp

@@ -1104,7 +1104,10 @@ public:
     }
 
     // One-shot extraction of vector from array (only requires extractvalue).
-    if (isa<VectorType>(resultType)) {
+    // Except for extracting 1-element vectors.
+    if (isa<VectorType>(resultType) &&
+        position.size() !=
+            static_cast<size_t>(extractOp.getSourceVectorType().getRank())) {
       if (extractOp.hasDynamicPosition())
         return failure();