[Telemetry] Send an event when users click on the "set as default browser" card in the settings page

[tdsmith]

Description & Product Manager / Data Scientist User Story

In order to understand whether we can improve the effectiveness of each messaging surface we’re testing in the set-default experiment (#18796), we should understand how many people interact directly with our message.

As a data scientist, I want to know, using a Glean event, if a user interacted with the "set as default browser" card in the settings page, which we will test in the branch described by #18376.

What questions will you answer with this data?

• How many people clicked on the message that we presented?
• When they set to default and the system dialog shows up, how many users actually set us as default?
  • How many people simply close the dialog and do not follow through with setting to default?

Acceptance Criteria

• ENG files a DS JIRA request outlining their methodology.
• DS sign off on instrumentation methodology addressing product questions.
• Event pings can be queried via re:dash
• Event pings can be queried via amplitude
• We are sending telemetry events for the actions listed in the requirements
• We have documented the telemetry
• We have asked a data steward to review the telemetry

┆Issue is synchronized with this Jira Task

[lobontiumira]

Verified as fixed on a debug Nightly build #2015805929, GV 89.0a1-20210418092832 with Google Pixel (Android 10):

• ping: a546b63f-afea-4a6e-9088-e56404bd0009
• the event is generated every time the user taps on the "Set as default browser" button from Settings - please see the attached photo
• Glean dashboard
• Logcat.txt

{
          "category": "set_default_setting_experiment",
          "name": "set_default_browser_clicked",
          "timestamp": 20399
        }