Add types to various low-level functions (#31781)

Adds types to various low-level modules. All changes are type-only, no
runtime changes. `tsc` now reports 38 less errors.

One problem was that `@types/sortablejs` does not accept promise return
in its functions which triggered the linter, so I disabled the rules on
those line.

web_src/js/features/repo-issue-list.ts

@@ -196,7 +196,7 @@ async function initIssuePinSort() {
 
   createSortable(pinDiv, {
     group: 'shared',
-    onEnd: pinMoveEnd,
+    onEnd: pinMoveEnd, // eslint-disable-line @typescript-eslint/no-misused-promises
   });
 }