ci: use CircleCI commands (angular#32745)

When we needed to run multiple commands in a reusable fashion, we needed to make a giant run block with multiple things inside. Using custom commands gives us a better way to do this.

See https://circleci.com/docs/2.0/reusing-config/#authoring-reusable-commands for more info.

PR Close angular#32745

Author: filipesilva