Combine Admin Add Account Request Flow into Instructor Account Request Flow

[ziqing26]

• Environment: master

Description of feature/enhancement

Before we introduced Account Request Form (#11878), admin add instructors in Admin Home Page (without the approve / reject stage) and the result is displayed as follows:

With the Account Request Form, admin can see pending account request submitted by instructors in a scrollable table. (see more in #12933)

Screen.Recording.2024-03-25.at.1.10.51.PM.mov

We want to combine the admin adding instructor flow into the instructor account request flow.

This will need:

1. Combine the old Result table and the new PendingAccountRequest table
2. Integrate the Approve / Reject stage for admin added request

Justification

Instead of having two separate table in admin home page for account requests added by admin and for those submitted by instructors, combining the UI into one table makes it cleaner and less confusing.