70343 Code sample small fixes (adopt a widget, cla: yes, d: api docs, f: material design, framework, waiting for tree to go green)

70379 Added Tabar Code samples (adopt a widget, cla: yes, d: api docs, d: examples, documentation, f: material design, framework, waiting for tree to go green)

70382 Update FlexibleSpaceBar dartpad sample (adopt a widget, cla: yes, d: api docs, d: examples, documentation, f: material design, framework, waiting for tree to go green)

71050 Add dartpad sample for AnimatedPadding (adopt a widget, cla: yes, d: api docs, d: examples, documentation, framework, waiting for tree to go green)

71093 AdoptAWidget: ColorFiltered (adopt a widget, cla: yes, d: api docs, d: examples, documentation, framework, waiting for tree to go green)