Pass the feature setting to DuoAgentPlatformModelMetadataService instead of generating it in service

The following discussion from !206527 (merged) should be addressed:

• @jpcyiza started a discussion: (+1 comment)

  @eduardobonet I think it's more straight forward to use the Ai::FeatureSettingSelectionService afterall. Getting it from ::Ai::DuoWorkflows::DuoAgentPlatformModelMetadataService is too weird of pattern. Let's get the same feature settings twice for now and refactor it later. So we can pass the backport MR (I think it's better to pass the feature setting rather then finding it in service IMO)