This follows Java naming conventions.

Normally we do not do merge commits. But this setup tries to preserve the history of
"fretboard" and our fork "experiments".

Before closing this issue, we should also document how to use this
script.

This class is modeled after PocketEndpointRaw from FFTV but adapted to:
- Take more dependencies as args instead of statically
- Use :concept-fetch
- Be more generic to more gracefully handle additional APIs

PocketEndpoint is intended to wrap this class and convert the raw JSON
into Kotlin types useful to the application.

See PocketEndpointRaw from FFTV:
  https://github.com/mozilla-mobile/firefox-tv/blob/daf118b092a7083cd41fdd51c5448fa41e4a885d/app/src/main/java/org/mozilla/tv/firefox/pocket/PocketEndpoint.kt#L75

This is intended to be passed in as a dependency to the endpoint classes
for them to know which urls to access.

This was adapted from Firefox for Fire TV's
BuildConfigDerivables.globalPocketVideoEndpoint:
https://github.com/mozilla-mobile/firefox-tv/blob/daf118b092a7083cd41fdd51c5448fa41e4a885d/app/src/main/java/org/mozilla/tv/firefox/utils/BuildConfigDerivables.kt#L30

This exposes two new testing only functions in `Glean`:
`testGetExperimentData` and `testIsExperimentActive`. This
additionally fixes Glean test code so that metrics clearing
only happens once.