Short-term string storage can cause problems when multiple translators are working on the same sim

In https://github.com/phetsims/rosetta/issues/446, it was reported that strings for a fully translated sim were not being shown in Rosetta's API for a specific translator. The explanation turned out to be that previously saved strings were being shown instead of the currently published strings. This reveals what I feel is a weakness in the current implementation. Rosetta allows users to save strings temporarily until a translation is ready to be fully submitted. However, if there are multiple translators working on the same sim, the strings saved in short-term storage can get out of sync with those that have been submitted for publication. Now that more translators are using Rosetta, this situation is likely to come up more often, and we should probably improve its behavior in this regard.

Start by reading issue #446 and tracing how Rosetta handles short-term saved strings versus currently published strings. Inspect the relevant storage and API entry points to understand how concurrent translators can see inconsistent data. Done means the behavior is defined and temporary strings no longer incorrectly override or conflict with published translations.