Re-work toHierarchy utility

Refactor `toHiearchy` to be more generic, performant

- Use callback to "pick" generic parent ID property instead of requiring that `pid` be hardcoded`
- Account for edge cases of an invalid parent ID
- Use Map to store node children for lookups
- Use one pass instead of removing empty nodes at the very end
- DX: use generics to type `toHierarchy`
- Make `toHierarchy` even more generic (reusable with `RecursiveList`)

Co-Authored-By: Bram <bramhavers@gmail.com>

types/utils/toHierarchy.d.ts

@@ -0,0 +1,21 @@
+type NodeLike = {
+  id: string | number;
+  nodes?: NodeLike[];
+  [key: string]: any;
+};
+
+/** Create a hierarchical tree from a flat array. */
+export function toHierarchy<
+  T extends NodeLike,
+  K extends keyof Omit<T, "id" | "nodes">,
+>(
+  flatArray: T[] | readonly T[],
+  /**
+   * Function that returns the parent ID for a given node.
+   * @example
+   * toHierarchy(flatArray, (node) => node.parentId);
+   */
+  getParentId: (node: T) => T[K] | null,
+): (T & { nodes?: (T & { nodes?: T[] })[] })[];
+
+export default toHierarchy;