50895 [flutter_tools] web cleanups (cla: yes, tool)

50904 [flutter_tools] cleanup build_tests to reduce mocking and globals usage (cla: yes, tool, waiting for tree to go green)

50925 Add parameter to Scaffold so its possible to disable open Drawer drag gesture (cla: yes, f: material design, framework, waiting for tree to go green)

50943 Ensure to close connection to VM after collecting coverage (cla: yes, tool)

50945 [flutter_tools] include LICENSE files as build dependencies (cla: yes, tool, waiting for tree to go green)

50948 Script to find Flutter earliest Flutter revision that contains an engine revision (cla: yes, team)