Desktop: Fixes #13346: Fix startup error when a non-English locale is selected

[personalizedrefrigerator]

Summary

This pull request fixes a "Refused to evaluate a string as JavaScript because 'unsafe-eval' is not an allowed source" startup error by pre-compiling plural localization forms. This error is a regression from d191349.

Fixes #13346.

Notes

• This pull request includes an automated regression test to verify that the app starts when the locale setting is set to fr_FR.
• The pluralForms field is now pre-compiled by build-translation.ts. To simplify review, this pull request includes only changes to locales/index.js and excludes the other updates made by yarn buildTranslations.
• The parsePluralForms function included an eslint-disable-next-line no-new-func. This seems to have been the only use of no-new-func.
• An alternate fix for Desktop: Startup error when using a non-English locale #13346 would be to git revert d1913493ab3a0850fafd14712508d8089f854cea. If this is done, it may still make sense to apply this pull request, since it resolves the "eventually we should automatically generate all the functions in advance in build-translations.ts" comment.

Testing plan

Desktop (Fedora 42)

1. Start Joplin.
2. Set the locale to "Français (France)" in settings.
3. Click "OK".
4. Verify that the locale has been changed.

This pull request includes an automated Playwright test.