fix: #3624920 Implement getTranslationLanguages() for the Display Builder 1.0.x head

Rajab Natshahrequested to merge
issue/webdashboard-3624920:3624920-translation-languages into 1.0.x

Closes #3624920

Implements getTranslationLanguages() in DashboardBuildable and DashboardOverrideBuildable, which the Display Builder 1.0.x head adds to DisplayBuildableInterface. Without it the site install fails with a fatal error.

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