Analytics docs clean up

[thekaveman]

Minor follow-ups to #953

In general this page is great and provides a lot of explanation of what our analytics are measuring. However it is written assuming familiarity with how Amplitude organizes event information. We want this language to be slightly more generic and descriptive for anyone unfamiliar with Amplitude.

Acceptance Criteria

• Alphabetize the Default user properties list
• Convert Default user properties list to table, similar to Custom user properties, with description and example values
• Describe app properties in Default user properties list: while these are captured under (Amplitude's) User Properties, they don't correspond to any real User info, instead describing the app itself:
  • Start version: First version of application identified for the user
  • Version: Current version of application identified for the user
  • Library: The Amplitude library used to send the event
• Split OS descriptor after : into description column of new table
• Update example value for referrer in Custom user properties table: this is a broken link for anyone clicking from the docs page
  • Use e.g. help page instead: https://benefits.calitp.org/help
• Fix link for Amplitude event documentation for Benefits, filtered by Core (currently points to Auth filtered events)
• Delete (e.g. Littlepay) from Enrollment event names

Additional context

Consider if we really want to link to the app multiple times from our docs. Especially given #1842 that links to the app directly from the landing page at the very top of the docs site.