Issue #3618263: A venue's sections, grades, configurations and pinnings cannot be reordered by dragging

Makes the four venue inventory lists draggable, the way the resource Tariffs tab already is.

WeightedOrderFormBase (in the engine, not in yoyaku_ui: yoyaku_placement depends on the engine and not on the admin UI module, so a base there could not be reached without a new module dependency) owns the draggable table, the renumber-from-zero on save and the empty case. Each list is then a subclass naming its columns, plus one line in its controller.

Left alone deliberately: places and pinned places. 1568 and 243 rows in one venue on the site this was checked against, and a place's weight is house order written by the numbering tool rather than something an operator arranges.

The test asserts what this module decides -- the list opens in the stored order, and a submitted arrangement is stored as a sequence from zero rather than as the numbers the selects held -- and not that core's tabledrag works.

Verified against a running site: dragging the last of 17 sections to the front stored 0,1,2,3,4 and the order was read back in that order.