We have a bunch of jobs that are built around the npm role, but
for projects using yarn, that can lead to ignoring yarn.lock.
For projects with a yarn.lock, we can assume the user wants to
use yarn. Make a new js-package-manager role that can detect
if that's the case and otherwise use npm. Make an js_build_tool
parameter that allows the user to override that auto-detection.
Make a whole new suite of jobs that do this behavior, do not have
npm in their name, and default to the latest node LTS, version 14.
Don't install yarn if we're not going to use yarn. Also allow people
who want to use yarn but don't have a yarn.lock to override
js_build_tool everywhere we do that logic.
Mark the old jobs deprecated.
Shift the npm and yarn roles to use the new js-package-manager role
with defaults set.
Change-Id: I8013228ca05607a69f390a9bb75991fc6543f865
202cce830e