PodcastIndexNamespace
Implements TierAwareFeedNamespaceInterface. Renders every podcast: (Podcasting 2.0) tag at channel and item level. Prefix podcast, URI https://podcastindex.org/namespace/1.0. Registered in core boot. Exposes its tag arrays to add-ons through the benecaster_feed_podcast_channel_tags filter (fired from channel_tags_for_tier(), which the tier-less channel_tags() delegates to with no tier and no episodes — so <podcast:trailer> is omitted there rather than guessed) and benecaster_feed_podcast_episode_tags (fired from episode_tags()). Replaces the deprecated PodcastNamespace shim.