refactor: replace use of mustache templates with edx-utils template

[navinkarkera]

Also removes underscore-min.js file which was unused

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[navinkarkera]

@farhan Could you please review these changes?

[farhan]

@farhan Could you please review these changes?

Sure, let me prioritize it.

[farhan]

Very good work overall in removing legacy code.

But it will be great if we could directly update the template library to Django Template Library rather than to Mako templates, because we have already parted ways with Mako templates and shifting the code to Django templates library.

ADR:
https://github.com/openedx/open-edx-proposals/blob/ba75a70d7b062426403667822978f101d71fce2d/oeps/best-practices/oep-0067/decisions/frontend/0005-django-templates.rst#L24

[itsjeyd]

@navinkarkera Friendly nudge to follow up on review feedback here.

[navinkarkera]

@itsjeyd Thanks for the reminder.

@farhan Thanks for reviewing this, I'll address your feedback soon (maybe next week).