Add typing for core-js string.prototype.padStart and padEnd (#22622)

* Add typing for core-js string.prototype.padStart and padEnd

* Change names to the ones in the core-js package docs

* Increment header version

* Update version

* Revert version change

types/core-js/index.d.ts

@@ -58,6 +58,8 @@ declare function $for<T>(iterable: Iterable<T>): $for<T>;
 
 interface String {
     at(index: number): string;
+    padStart(length: number, fillStr?: string): string;
+    padEnd(length: number, fillStr?: string): string;
 }
 
 interface Object {