llvm_tools: merge update_packages_*.py files

Merge update_packages_and_run_tryjobs.py and
update_packages_and_test_cq.py as the two modules share much command
code.

BUG=chromium:1001602

TEST=local tests.

Change-Id: Iac957ea77af4257e454fec99ff13424e778ec51a
Reviewed-on: https://chromium-review.googlesource.com/c/chromiumos/third_party/toolchain-utils/+/2148478
Reviewed-by: Manoj Gupta <manojgupta@chromium.org>
Tested-by: Jian Cai <jiancai@google.com>
7 files changed