patch 9.1.0200: `gj`/`gk` not skipping over outer virtual text lines

patch 9.1.0200: `gj`/`gk` not skipping over outer virtual text lines

Problem:  `gj`/`gk` was updating the desired cursor virtual column to
          the outer virtual text, even though the actual cursor position
          was moved to not be on the virtual text, leading the need to
          do an extra `gj`/`gk` to move past each virtual text line.
          (rickhowe)
Solution: Exclude the outer virtual text when getting the line length
          for moving the cursor with `gj`/`gk`, so that no extra
          movement is needed to skip over virtual text lines.
          (Dylan Thacker-Smith)

fixes: #12028
related: #14262

Signed-off-by: Dylan Thacker-Smith <dylan.ah.smith@gmail.com>
Signed-off-by: Christian Brabandt <cb@256bit.org>