* For https://github.com/mozilla-mobile/fenix/issues/3088: add translation pruning Py scripts from Focus
The only change made was updating "Focus/Klar" to "Fenix"
* For 3088: call translation pruning scripts during release builds
* For 3088: fix filter-release-translations.py
Moving it into Fenix introduced one additional layer of nesting, which was not accounted for in a relative path. 🤦
* For 3088: comment about the risks of modifying source
* For 3088: updated locales.py to read from l10n.toml
Also removed some previously unused properties from locales.py
* For 3088: added error handling to script in locales.py
* For 3088: updated locale parser per review comments
It was fixed in [1], but I regressed it when I resolved conflicts in [2]
[1] f9863564ee\#diff-3a2aaafc93fc8bb53e2029001aa236aeL98
[2] 2b941e690b\#diff-3a2aaafc93fc8bb53e2029001aa236aeR95
