[landing] repurpose InfoBlock component

Summary:
This diff repurposes the InfoBlock component to work for this landing page redesign. A big change with this InfoBlock component is that we no longer need an image, and all the content in the InfoBlock is centered. Here is a screenshot of the designs for extra context:

Depends on D8078

Test Plan:
Please see the demo videos/screenshots below to see how the new InfoBlock component:

Desktop/Responsive:

Tablet:

Mobile:

Reviewers: atul, kamil

Reviewed By: atul

Subscribers: ashoat, tomek

Differential Revision: https://phab.comm.dev/D8079