29772 Roll to CanvasKit 0.31.0 (cla: yes, platform-web, needs tests)

29792 [web] Fail if Skia Gold is required but unavailable (cla: yes, waiting for tree to go green, platform-web, needs tests)

29801 [web] move browser installation to BrowserEnvironment.prepare (cla: yes, platform-web, needs tests)

29847 [web] Use fuzzy matching in Gold (cla: yes, platform-web, needs tests)

29888 [web] Fixing text foreground paint / stroke for HTML web-renderer (cla: yes, waiting for tree to go green, platform-web, needs tests)

29896 [web] merge the README files into one (cla: yes, platform-web)