feat: Added Canvas support

[arslanashraf7]

Related Ticket:

https://github.com/mitodl/open-edx-plugins/issues/6

Side Note 1: Once this PR is merged we'll be adding only that code which would be part of this PR(and probably future cherry-picks) instead of this whole chunk

What's this PR do?

• It removes the remote_gradebook and its dependencies
• It extracts the canvas_integration into a separate plugin
• Keeps only canvas_integration plugin supporting counterpart(Mostly instructor functionality that the canvas depended upon)

How to test?

This might need a counterpart a plugin to completely test. The counterpart to test this PR with is currently a WIP (https://github.com/mitodl/open-edx-plugins/pull/8). Once that PR is finalized we can test this one:

• Setup this branch of the platform
• Install the plugin from https://github.com/mitodl/open-edx-plugins/pull/8 (e.g. put that plugin inside dir in /src dir & then move to make lms-shell & then pip install /edx/src/dist/<plugin>) OR any other way suitable
• make dev.provision.lms/make lms-restart
• Open any course as Admin & open instructor tab
• You should see a Canvas tab under the instructor tab
• Clicking Canvas tab should enable you to test the canvas functionality

[arslanashraf7]

@gsidebo This also requires your review if possible, This is the corresponding PR for ol-openedx-canvas-integration