refactor: tailwind equivalent unit dropdown

[jayant31j]

As part of front-end migration. I migrated all the fx-layout fields to tailwind classes

Changes made:
Used tailwind components to replace the older fx-layout component in html file of Unit dropdown.

Description

Replaced fx-layout components of the Unit dropdown to tailwind. The unit dropdown can be seen from the tutor and student ontrack systems.

• Before Screenshot:

• After screenshot

Type of change

Please delete options that are not relevant.

• Breaking change (fix or feature that would cause existing functionality to not work as expected)

Testing Checklist:

• Tested in latest Chrome
• Tested in latest Safari

Checklist:

• My code follows the style guidelines of this project
• I have performed a self-review of my own code
• I have commented my code in hard-to-understand areas
• I have made corresponding changes to the documentation
• My changes generate no new warnings
• I have requested a review from @macite and @jakerenzella on the Pull Request

[maddernd]

I have made an upstream PR for this one.

[maddernd]

This does not work, none of the styling is applied correctly based on this PR and it does not match the screenshots.