zephyr: Export coverage metrics in CQ build
zephyr: Export coverage metrics in CQ build

When running tests for the zephyr coverage cq build, put coverage data
into the FwTestMetricList proto.

BRANCH=None
BUG=b:231639771
TEST=firmware_builder.py --metrics /tmp/metrics --code-coverage test
cat /tmp/metrics

Cq-Depend: chromium:3642959
Signed-off-by: Jeremy Bettis <4df7b5147fee087dca33c181f288ee7dbf56e022@google.com>
Change-Id: I07902138d2cb1b75d08bad49accf8fe2f2049b8e
Reviewed-on: https://chromium-review.googlesource.com/c/chromiumos/platform/ec/+/3642541
Commit-Queue: Tristan Honscheid <1e17951ff5ffc8afe254954c03de64afef62fe52@google.com>
Reviewed-by: Tristan Honscheid <1e17951ff5ffc8afe254954c03de64afef62fe52@google.com>
Tested-by: Jeremy Bettis <4df7b5147fee087dca33c181f288ee7dbf56e022@chromium.org>

coreboot/chrome-ec,coreboot/chrome-ec,coreboot/chrome-ec,coreboot/chrome-ec,coreboot/chrome-ec,coreboot/chrome-ec