lib: refactor to use primordials in lib/assert.js

PR-URL: nodejs#41702
Reviewed-By: Darshan Sen <raisinten@gmail.com>
Reviewed-By: Antoine du Hamel <duhamelantoine1995@gmail.com>
Reviewed-By: James M Snell <jasnell@gmail.com>
Reviewed-By: Mestery <mestery@protonmail.com>

Author: marsonya

lib/assert.js

@@ -965,10 +965,10 @@ assert.ifError = function ifError(err) {
       // This will remove any duplicated frames from the error frames taken
       // from within `ifError` and add the original error frames to the newly
       // created ones.
-      const origStackStart = origStack.indexOf('\n    at');
+      const origStackStart = StringPrototypeIndexOf(origStack, '\n    at');
       if (origStackStart !== -1) {
         const originalFrames = StringPrototypeSplit(
-          origStack.slice(origStackStart + 1),
+          StringPrototypeSlice(origStack, origStackStart + 1),
           '\n'
         );
         // Filter all frames existing in err.stack.