PersonaBar pages become unresponsive with 2000 pages on Expand/Collapse

[nadeem-akhtar-nu]

Description of bug
PersonaBar > pages become unresponsive on expand/collapse of a tree view node with 2k children

Preconditions
A page contains 2000+ child pages.

Steps to reproduce

• Login to the site with admin privileges
• Go to Persona bar->Content-> Pages
• Click on the [+] icon for page having 2000+ children in order to expand the page tree view.
• The site takes too long to open and throws a Page Unresponsive error.
• Similar slowness occurs when try to collapse the page tree view node.

Current behavior
The site takes too long to open and throws a Page Unresponsive error.

Expected behavior
The pages should expand and open without an error. Subsequently, parent node should collapse and close without an error.