fix: remove setting defaults in ssr from useDefaultLocale

[herkulano]

Closes #7344

✅ Pull Request Checklist:

• Included link to corresponding React Spectrum GitHub Issue.
• Added/updated unit tests and storybook for this change (for new code or code which already has tests).
• Filled out test instructions.
• Updated documentation (if it already exists for this component).
• Looked at the Accessibility Practices for this feature - Aria Practices

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[snowystinger]

So I don't think we want to completely remove this. Instead, we want to split the I18nProvider's internals into two components, one which calls the useDefaultLocale and one which doesn't. This is how to conditionally call hooks since they can't be in an if statement.

Which component we call inside the I18nProvider should be determined by if the locale prop is passed to the I18nProvider.

see proposal here: #7344 (comment)

Side note, if you've done it this way instead intentionally, can you explain your decision?

[herkulano]

Sorry, made the changes to split the provider.

[herkulano]

Although the currentLocale is set to the default en-US even on SSR:

let locale = typeof window !== 'undefined' && window[localeSymbol]
    // @ts-ignore
    || (typeof navigator !== 'undefined' && (navigator.language || navigator.userLanguage))
    || 'en-US';

So setting a default on SSR in the useDefaultLocale feels unnecessary.

[herkulano]

After trying the provider split I realized that we need to re-render on languagechange and removing the useDefaultLocale() hook entirely from the provider breaks components like NumberField that require a re-render when changing language: https://app.circleci.com/pipelines/github/adobe/react-spectrum/27484/workflows/dad88c6d-a527-49a0-bad5-02a412732311/jobs/470813

I now believe the initial approach was correct and we don't need to split the provider as the useDefaultLocale() is necessary even if the locale is set in the provider. I believe the extra re-render comes from returning the default locale on SSR.