Tweaks to DataTable generics (#1968)

Adjust DataTable types.
- Make key in `cell` slot prop less strict to prevent type errors in markup.
- Resolve property path names up to one level deep for header keys.

types/DataTable/DataTableTypes.d.ts

@@ -0,0 +1,17 @@
+type PathDepth = [never, 0, 1, 2, ...0[]];
+
+type Join<K, P> = K extends string | number
+  ? P extends string | number
+    ? `${K}${"" extends P ? "" : "."}${P}`
+    : never
+  : never;
+
+export type PropertyPath<T, D extends number = 10> = [D] extends [never]
+  ? never
+  : T extends object
+  ? {
+      [K in keyof T]-?: K extends string | number
+        ? `${K}` | Join<K, PropertyPath<T[K], PathDepth[D]>>
+        : never;
+    }[keyof T]
+  : "";