[User Interview Results] Make data source drop-down items more clear

[emtwo]

Three things can be done to improve the clarity here:

1. Data source names should refer to the content of the data rather than (or in addition to) the name of the datastore (e.g. perhaps "Desktop User Telemetry (Athena)" instead of simply "Athena")

2. Some documentation already exists that can simply be linked inside of the Redash UI to show what the data schema for a given data source looks like. E.g. https://firefox-source-docs.mozilla.org/toolkit/components/telemetry/telemetry/data/main-ping.html

3. Link to a set of examples using this data source. These could be queries living in Redash that are created and reviewed by "trusted authorities". Some such examples exist within Redash already but they are very difficult to discover.

[rafrombrc]

This all points to a bigger issue, which is that we need to both store and show more complete / better metadata on the data sources. We could tackle this piecemeal, but I think it makes more sense to be thought of as a bigger, well thought out initiative. We're currently handling both react migration and extensions stuff, this will go in the queue for one of the next bigger things we work on.

[rafrombrc]

Related: #372