Refactor RegionsHighlighter to share regexes

Instead of storing regexes in each regions, move them to the core
highlighter in a hash map so that shared regexes between different
regions are only applied once per update instead of once per region

Also change iteration logic to apply all regex together to each
changed lines to improve memory locality on big buffers.

For the big_markdown.md file described in #4685 this reduces
initial display time from 3.55s to 2.41s on my machine.

0 files changed, 0 insertions, 0 deletions