Use the same tab switcher for "My Courses" page as the "Learners Profile" page

### Is your feature request related to a problem? Please describe
In Learner's Profile page, the learner's active courses listing uses a tab switcher (https://github.com/Automattic/sensei/blob/ebcbc6112654e85db00edb71685cf0fdf7a8aacd/assets/js/user-dashboard.js) that allows user to switch tabs between active and completed courses without reloading the page.

However, the My Courses page does not use this tab switcher and requires reloading when changing tabs

### Describe the solution you'd like
Use the same tab switcher on My Courses page compared to the Learner's Profile page.

### Additional context
Originally requested in https://wordpress.org/support/topic/students-profile/

Start with assets/js/user-dashboard.js, which contains the tab switcher used on the Learner Profile page, then locate the corresponding My Courses page implementation. Reuse that behavior so active and completed courses switch without a reload, and verify both tabs display the expected listings.

Written by the indexing model from the issue text.