More comfortable and safe resource name translation without breaking translation freeze.

Throw a reference error instead of silently using an untranslated string if someone would have passed a non-existing translation context.
Throw a property undefined warning if someone passed a non-existing resource when trying to translate it.
Both warnings had been introduced in rP16127, were removed by rP18964 but now occur without adding code explicitly.

Differential Revision: https://code.wildfiregames.com/D625
Reviewed By: s0600204