TimeseriesPanel: Preserve string fields for data link interpolation (#58424)

* TimeseriesPanel: Preserve string fields for data link interpolation

* clean code

* Modify tests so that string fields are allowed only when a valid time/number dataframe exists

* performance mods

* fix wrong length

* remove console.log

* Check if aligned dataframe has links

packages/grafana-data/src/vector/SortedVector.ts

@@ -23,4 +23,8 @@ export class SortedVector<T = any> implements Vector<T> {
   toJSON(): T[] {
     return vectorToArray(this);
   }
+
+  getOrderArray(): number[] {
+    return this.order;
+  }
 }