Separate release locale list from master locale list.

[person808]

We use l10n.toml to define what locales to include in our builds. For release we want to use a separate list of locales than on the master branch. To allow us to have the same l10n.toml file on master and release branches we should create a separate list that is used to filter out locales on release builds. We can't modify this list on master because Pontoon uses it to expose locales to translators.

┆Issue is synchronized with this Jira Task

[person808]

Note for QA: we want to check that the apk from here should have only the locales in l10n-release.toml in the Settings > Languages screen. If we can verify the locale filter is running on one build in TC then it should be working for all build variants its needed for.

[lobontiumira]

Verified all the languages from the locales in l10n-release.toml, on the build from here with OnePlus 5T (Android 9).
Three languages are missing on the build from above, but they are available on the 7/27 Nightly build:

1. Hebrew "he".
2. Bahasa Indonesia "id".
3. Triqui "trs".

I'll remove the qa:needed label for now.
@person808 please let us know if there is anything else we can do.
Thanks!

[person808]

Likely just a delay in pulling in the translations thanks!