test/run_device_tests.py: Add utils unit test
test/run_device_tests.py: Add utils unit test

Also allow specifying the timeout on a per-test basis. The utils unit
test takes longer than the other tests to run.

BRANCH=none
BUG=b:155230812
TEST=With dragonclaw v0.2 connected to Segger J-Trace and servo micro:
     ./test/run_device_tests.py -t utils

Signed-off-by: Tom Hughes <fc5c12f30a5ed2baa0581f44ee14ad1eb7b20d83@chromium.org>
Change-Id: I3b7368a4e4178f8371fae1155cf7dc457578dad0
Reviewed-on: https://chromium-review.googlesource.com/c/chromiumos/platform/ec/+/2248713
Reviewed-by: Yicheng Li <77a205905d8955597c069555e9569c30512f6bd8@chromium.org>

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