Add filter options to following feed (resolves #726)

What does this PR do?

Adds filters for non-public notes, quotes, replies, and files to the following feed. These options are shared with the user feed and added to the filter menu that already exists. The following feed and user feed are extended to support a shared superset of filters, ensuring that both sides are always in sync. All filter selections are saved to the frontend state to persist between loads.

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