This switches the static asset check over from the deprecated
paver commands to the new 'npm run build' command. Doing so allows us
to check both the prod AND dev build, whereas before we were only
checking the prod build.
Please note that, as before, the "check" is only ensuring that the build
returns 0. It is not checking the contents of the build output.
Closes: https://github.com/openedx/edx-platform/issues/34834
69e5fa4227
