Closes #1194: Adds search shortcut telemetry

[sblatz]

Please refer to just this commit for review, as this is currently blocked on merging #882.

[sblatz]

Request for data collection review form

All questions are mandatory. You must receive review from a data steward peer on your responses to these questions before shipping new data collection.

1. What questions will you answer with this data?

• How do users engage with the search shortcuts feature?
• Do users who open the search shorcut engine page follow through to actually making a search with a different engine?

2. Why does Mozilla need to answer these questions? Are there benefits for users? Do we need this information to address product or business requirements?

• We would like to know the engagement level of our shortcuts feature. Based on these metrics, we can gauge the utility of a feature like this and choose to improve or remove it in the future.

3. What alternative methods did you consider to answer these questions? Why were they not sufficient?

• N/A (These are baseline metrics)

4. Can current instrumentation answer these questions?

• Currently no, as these are some of the first metrics we're recording

5. List all proposed measurements and indicate the category of data collection for each measurement, using the Firefox data collection categories on the found on the Mozilla wiki.

• All data is Category 2.

6. How long will this data be collected?

• @mmccorks will permanently monitor this data.

7. What populations will you measure?

• All release, beta, and nightly users with telemetry enabled.

8. Please provide a general description of how you will analyze this data.

• Glean

9. Where do you intend to share the results of your analysis?

• Only on Glean and with mobile teams.

[colintheshots]

Is this almost the same PR, but with telemetry added?