feat(metrics): Log which marketing material is shown to a user.

* Add `marketingType`, `marketingLink`, `marketingClicked`.
* `marketingType` is either `android-sync` or `survey`
* `marketingLink` is the URL that the user can click on.
* `marketingClicked` is whether the user clicked on the marketing.

fixes #1259
Merge pull request #1357 from mozilla/issue-1259-promotion-metrics

feat(metrics): Log which marketing material is shown to a user.