[autotest] platform_BootPerfServer uploads perf data to new perf dashboard

Read the perf data from keyval file. Call output_perf_value()
to upload the perf data to chromeos perf dashboard.

Uploading is controlled by a tag 'upload_perf' passed from control file.
Only control.perfalearts will be uploading perf data.

Also make client/common_lib/base_utils:read_keyval
respect type_tag in the key noted in '{}', e.g. 'seconds_reboot_time{perf}'.

BUG=chromium:280634
TEST=Ran the test locally, confirmed that the file "perf_measurements"
with correct perf data was outputted to the result dir.

Change-Id: Id71624ea344c69e4b2efc9535436ecb0af88a187
Reviewed-on: https://chromium-review.googlesource.com/174413
Reviewed-by: Richard Barnette <jrbarnette@chromium.org>
Tested-by: Fang Deng <fdeng@chromium.org>
Commit-Queue: Fang Deng <fdeng@chromium.org>
4 files changed