Canvas text: fix ellipsis RTL handling

Canvas text: fix ellipsis RTL handling

First, fixing ellipsis text positions: ellipsis items should be assigned the
text positions of the omitted text (while maintaining the formatting of the
last visual item). In the case where an entire item was rejected, it
will be assigned that item's text position. If an item was split, it will be
assigned the text position of the split portion.
The BiDi reorder code relies on properly-assigned text positions.

Second, fixing ellipsis handling: the width calc was only considering the
ellipsis item's width. However, if the ellipsis is placed as e.g. the first
visual item (such as in RTL cases), its advance value should've be considered,
instead.

Thanks Youngbok Shin for the test case and information.

@fix