Changed default language codename can crash sync run

[pokornyd]

Brief bug description

If a default language's codename from sync snapshot differs from the default lang codename in the target environment and, simultaneously, another language from the snapshot references the default language as a fallback, the sync run fails with The specified fallback language is inactive or does not exist.

This is most likely an ordering issue, where the languages referencing the default language are upserted before the patch operations renaming the default language take place. See screenshot for reference

Repro steps

1. Have an empty target environment
2. Have a source environment where the default language codename is other than default and has other languages using the default language as fallback
3. Try syncing the models between the two environments
4. ???
5. Profit

Expected behavior

...it works.