gather_builder_stats.py: add advanced flags to skip upload/carbon/gather
gather_builder_stats.py: add advanced flags to skip upload/carbon/gather

This change adds --no-upload, --no-carbon, and --no-mark-gathered
optional command line flags to gather_builder_stats.py, which are
useful for testing purposes especially when adding a new class of
statistics.

BUG=chromium:367869
TEST=None

Change-Id: Icb82cd42b5c44655184a275061a1f8e16d3a5355
Reviewed-on: https://chromium-review.googlesource.com/197507
Reviewed-by: Aviv Keshet <178e8ae417efbe404feca7ab4cb8f0ba8c109369@chromium.org>
Tested-by: Aviv Keshet <178e8ae417efbe404feca7ab4cb8f0ba8c109369@chromium.org>

chadversary/chromiumos.chromite,bpsinc-native/src_third_party_chromite,chadversary/chromiumos.chromite,bpsinc-native/src_third_party_chromite,bpsinc-native/src_third_party_chromite