Setup testing track on Google Play

[pocmo]

Build, sign and upload Nightly builds to Google Play testing track.

┆Issue is synchronized with this Jira Task

[pocmo]

This should build and upload:

• nightlyArmRelease
• nightlyAarch64Release
• nightlyX86Release

[pocmo]

Depends on #60.

[JohanLorenzo]

That's also tracked at https://bugzilla.mozilla.org/show_bug.cgi?id=1478220.

What Google Play track would you like to use, @pocmo? The custom one "nightly", like the one we have on Focus?

[pocmo]

What Google Play track would you like to use, @pocmo? The custom one "nightly", like the one we have on Focus?

Yeah, exactly the same setup like Focus Nightly (with access via google group).

[JohanLorenzo]

* nightlyAarch64Release

@pocmo told me we don't want to ship this architecture just yet.