S&R: Fix Look-ahead & behind highlighting & replace

Merged Kåre Särs requested to merge work/fix_lookahead_lookbehind_highlight_replace into master

Strip the look-ahead and look-behind from the regular-expression that checks if a string has been modified after search and returns the possible captures. We strip the look-ahead/behind because we only match against the previously found range.

BUG: 449545

Merge request reports