Refinement to commit cdba7fef attachment of port to component on diagram

umbrello/widgets/portwidget.cpp
- In function moveWidgetBy(),
  - If port is at left or right edge of owner then
    - If newX is smaller than owner->x() - width() then clip newX to
      owner->x() - width()
    - If newX is greater than owner->x() + owner->width() then clip newX to
      owner->x() + owner->width()
  - If port is at top or bottom edge of owner then
      - If newY is smaller than owner->y() - height() then clip newY to
        owner->y() - height()
      - If newY is greater than owner->y() + owner->height() then clip newY
        to owner->y() + owner->height()
- In function attachToOwningComponent(),
  - If scenePos.x() is in the range
      [ owner->x() - width() : owner->x() + owner->width() ]
    then use scenePos.x() unmodified in call to setX().
  - If scenePos.y() is in the range
      [ owner->y() - height() : owner->y() + owner->height() ]
    then use scenePos.y() unmodified in call to setY().

Known issue:
On moving a ComponentWidget, its attached PortWidgets should move along.

CCBUG:115269