flutter: add beta and dev channels
flutter: artifacts are now downloaded in $HOME/.cache/flutter
flutter: remove all artifacts from flutter
flutter: fix lockfile path
flutter: fix pub_cache
flutter: fix flutter_tools/.packages pointing to /build
flutter: clean patches
flutter: fix write error on .cache/flutter/lockfile
flutter: add zlib as a dependency
flutter: add missing dependencies
flutter: fix flutter version
flutter: update versions + dependencies
