Fullscreen MediaViewer refactor

- Moved media related logic into notedeck instead of the ui crate,
  since they pertain to Images/ImageCache based systems

- Made RenderableMedia owned to make it less of a nightmware
  to work with and the perf should be negligible

- Added a ImageMetadata cache to Images. This is referenced
  whenever we encounter an image so we don't have to
  redo the work all of the time

- Relpaced our ad-hoc, hand(vibe?)-coded panning and zoom logic
  with the Scene widget, which is explicitly designed for
  this use case

- Extracted and detangle fullscreen media rendering from inside of note
  rendering.  We instead let the application decide what action they
  want to perform when note media is clicked on.

- We add an on_view_media action to MediaAction for the application to
  handle. The Columns app uses this toggle a FullscreenMedia app
  option bits whenever we get a MediaAction::ViewMedis(urls).

Signed-off-by: William Casarin <jb55@jb55.com>

crates/notedeck_ui/src/lib.rs

@@ -1,13 +1,11 @@
 pub mod anim;
 pub mod app_images;
-pub mod blur;
 pub mod colors;
 pub mod constants;
 pub mod context_menu;
-pub mod gif;
 pub mod icons;
 pub mod images;
-pub mod jobs;
+pub mod media;
 pub mod mention;
 pub mod note;
 pub mod profile;