i18next / react-i18next / 34764615523

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fix: refresh the returned i18n wrapper when resolvedLanguage changes

The wrapper is a snapshot of the instance (#1863), cached since #1885 so its
identity only changes when the language state does. That cache was keyed on
i18n.language alone, narrower than the three fields the surrounding useMemo
depends on, so a resolvedLanguage (or languages) change of its own kept handing
components the previous snapshot.

That happens whenever the translations for the current language arrive after the
switch: i18next resolves to the fallback while its store is still empty for it,
and re-resolves once the resources are there without language changing again.
Components reading i18n.resolvedLanguage - language switchers, for example -
then stayed one switch behind.

The cache key now covers language, resolvedLanguage and languages, so wrapper
identity still only changes when the language state changes and the caching from
#1885 is unaffected.

Reported via i18next/next-i18next#2348

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