4175 [camera_web] Add availableCameras implementation (cla: yes, waiting for tree to go green, p: camera, platform-web)

4182 [camera_web] Add createCamera implementation (cla: yes, waiting for tree to go green, p: camera, platform-web)

4185 [shared_preferences_web] Migrate tests to integration_test (cla: yes, waiting for tree to go green, p: shared_preferences, platform-web)

4186 [camera_web] Add initializeCamera implementation (cla: yes, waiting for tree to go green, p: camera, platform-web)

4190 [camera_web] Add buildPreview implementation (cla: yes, waiting for tree to go green, p: camera, platform-web)

4196 [camera_web] Add takePicture implementation (cla: yes, waiting for tree to go green, p: camera, platform-web)