[OpenMP][Clang][NFC] Initializer all of ScanInfo member variables and add deleted copy ctor and assignment operator (#158130)

Static analysis flagged that we were not initializing all of the members
of ScanInfo, fix this so that they are all initialized. Also it pointed
out that we were not following the rule of three. We had a custom
destructor but not copy constructor or assignment. We should never copy
or assignment so defaulting them as deleted.

Author: shafik

llvm/include/llvm/Frontend/OpenMP/OMPIRBuilder.h

@@ -4001,15 +4001,17 @@ class ScanInfo {
 
   /// Keeps track of value of iteration variable for input/scan loop to be
   /// used for Scan directive lowering
-  llvm::Value *IV;
+  llvm::Value *IV = nullptr;
 
   /// Stores the span of canonical loop being lowered to be used for temporary
   /// buffer allocation or Finalization.
-  llvm::Value *Span;
+  llvm::Value *Span = nullptr;
 
   ScanInfo() {
     ScanBuffPtrs = new llvm::SmallDenseMap<llvm::Value *, llvm::Value *>();
   }
+  ScanInfo(ScanInfo &) = delete;
+  ScanInfo &operator=(const ScanInfo &) = delete;
 
   ~ScanInfo() { delete (ScanBuffPtrs); }
 };