message: Add mlir::Function::eraseBody helper to remove the body of a function.
  This does not add any new functionality but gives clearing the blocks of the
  body region a more obvious name.
diff: @@ -88,6 +88,7 @@ public:
  //===--------------------------------------------------------------------===//
  Region &getBody() { return body; }
  + void eraseBody() { body.getBlocks().clear(); }
  /// This is the list of blocks in the function.
  using RegionType = Region::RegionType;
  