Refactor WrapHighlighter::next_split_pos to avoid non-linear complexity
Refactor WrapHighlighter::next_split_pos to avoid non-linear complexity

Previous Implementation was constantly computing byte/column count
from the begining of the line, leading to a non-linear complexity
with respect to the length of a line.

Fixes #2146

occivink/kakoune,alexherbo2/kakoune,danr/kakoune,alexherbo2/kakoune,lenormf/kakoune,Somasis/kakoune,Somasis/kakoune,mawww/kakoune,occivink/kakoune,alexherbo2/kakoune,mawww/kakoune,jkonecny12/kakoune,occivink/kakoune,mawww/kakoune,danr/kakoune,danr/kakoune,casimir/kakoune,jkonecny12/kakoune,occivink/kakoune,casimir/kakoune,jkonecny12/kakoune,casimir/kakoune,jkonecny12/kakoune,lenormf/kakoune,danr/kakoune,mawww/kakoune,jjthrash/kakoune,casimir/kakoune,Somasis/kakoune,alexherbo2/kakoune,Somasis/kakoune,lenormf/kakoune,jjthrash/kakoune,lenormf/kakoune,jjthrash/kakoune,jjthrash/kakoune