- refactor the `experimentation/utils.js` file a bit to make room for
  another function making use of the same experiments data
- add `getAllExperimentContexts` function to the `experimentation/utils`
  module
- use the new `getAllExperimentContexts` function as part of the
  `initDefaultTrackers` function in the `tracking/index.js` file to
  include a `gitlab_experiment` context for each experiment on the page
- update specs to reflect the changes