message: Add a getContext() convenient accessor on mlir::Value (NFC)
diff: @@ -52,6 +52,9 @@ public:
  Type getType() { return typeAndKind.getPointer(); }
  + /// Utility to get the associated MLIRContext that this value is defined in.
  + MLIRContext *getContext() { return getType().getContext(); }
  +
  /// Mutate the type of this Value to be of the specified type.
  ///
  /// Note that this is an extremely dangerous operation which can create
  