Fix the patterns for code blocks and the handling of newlines when matching patterns - #9921

Fix the patterns for code blocks and the handling of newlines when matching patterns#9921

srawlins merged 2 commits into

flutter:masterflutter/devtools:masterfrom

DanTup:fix-span-parser-newline-handlingDanTup/devtools:fix-span-parser-newline-handlingCopy head branch name to clipboard