93086 Improve tracing (team, framework, f: material design, f: scrolling, cla: yes, waiting for tree to go green, integration_test)

94613 fix small typo in doc of SingleChildScrollView (framework, f: scrolling, cla: yes, waiting for tree to go green)

94772 Prefer .of to .from (framework, a: animation, f: material design, a: accessibility, f: scrolling, f: cupertino, f: routes, f: gestures, f: focus)

94834 Add explicit null returns in flutter/test (a: text input, framework, f: material design, f: scrolling, f: cupertino, f: routes, waiting for tree to go green)

95044 Fix some issues with samples (team, framework, f: material design, f: scrolling, d: api docs, d: examples, waiting for tree to go green, documentation)