Atest: send saved time of acloud_create to metrics.

This CL enables 2 detect types for storing the duration of acloud create
and find+build, and send the duration to metrics unless --no-metrics is
passed.

Bug: 160390329

Test: m clean
  atest-src -v --start-avd hello_world_test
  # will see 'Totally saved 232s.'

  atest-src -v --start-avd hello_world_test
  # will see 'Totally saved 4s.'

Change-Id: I3ea0c5f65da39da4c2f4316133e2c3814b9a4562
3 files changed