Move the filter bar and the timeline onto the library's Slint global

The date-range fields and their band on the capture-time axis, the
timeline's bars, labels, scrub/pinch/pan/zoom callbacks and its
sweep/current-bucket/anchored state, and the filter bar's people chips,
mode, eyes-open toggle and gesture reference move from AppWindow onto the
`Library` global. Rust reaches them through window.global::<Library>()
rather than window.set_/get_/on_ on the root, as the earlier commits on
this branch did for the grid's cells, selection, ratings and keywords.

ui/dr-ui/src/collections_ui/wiring_grid.rs

@@ -112,7 +112,7 @@ fn wire_selection(
                 // Where the window starts, so the press is recorded as the ordinal
                 // it is rather than as a row that stops meaning this photograph on
                 // the next scroll.
-                let offset = w.get_library_offset().max(0) as usize;
+                let offset = w.global::<Library>().get_library_offset().max(0) as usize;
                 select_row(&w, &ctl, &ids, offset, row as usize, ctrl_held, shift_held);
 
                 // TRACES: FR-UI-2 | FR-UI-4 | FR-CAT-7