[ci] Move Android build-all CI to heavy workload (#4624)
[ci] Move Android build-all CI to heavy workload (#4624)

This task's memory usage is very close to the 4GB limit of the light-workload machines, and sometimes goes over and causes flaky failures.
flutter/plugins,flutter/plugins,flutter/plugins,flutter/plugins,flutter/plugins,flutter/plugins,flutter/plugins,flutter/plugins