43739 enable avoid_web_libraries_in_flutter (cla: yes, framework)

43742 Adjust and refactor all FlatButton tests into its respective file (cla: yes, f: material design, framework, waiting for tree to go green)

43745 Run update packages –force-upgrade (cla: yes, team)

43748 Gold Performance improvements (a: tests, cla: yes, framework, team)

43753 pass –no-gen-bytecode to aot kernel compiler invocations (cla: yes, tool)

43756 Mark routes as opaque when added without animation (a: animation, cla: yes, f: inspector, f: routes, framework)

43758 Split desktop config fallback variable by platform (a: desktop, cla: yes, tool)