patch 9.1.0129: Fix truncation of text_wrap 'wrap' virt text after EOL list char

patch 9.1.0129: Fix truncation of text_wrap 'wrap' virt text after EOL list char

Problem:  Virtual text with text_wrap 'wrap' was effectively being
          truncated by a break conditional on the EOL list character
          being added to the screen line. (BigPeet)
Solution: Remove the condition that was leading to the early break and
          instead fix a similar but incorrectly written outer condition
          that checks if there is more to add at the end of the screen
          line. (Dylan Thacker-Smith)

Also, related:
- update comment in win_line()
- remove no longer necessary at_end_str variable in win_line()

fixes: #12725
closes: #14079

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