73352 Deprecated obsolete Material classes: FlatButton, RaisedButton, OutlineButton (cla: yes, f: cupertino, f: material design, framework, waiting for tree to go green)

73353 [flutter_tools] delegate first run message re-display to new class, only if changed (cla: yes, tool, waiting for tree to go green)

73357 [flutter_tools] prevent NPE due to moved/deleted packages during upgrade packages (cla: yes, tool, waiting for tree to go green)

73361 Add material icons golden test (cla: yes, f: material design, framework, will affect goldens)

73364 [flutter_tools] delete .packages during flutter clean (cla: yes, tool, waiting for tree to go green)