[core][docs] Revise the Container docs

[mapache-salvaje]

Part of #35158

The Container doc (shared by Material UI and MUI System) is pretty sparse, and doesn't give the reader a very good idea of why to choose this component over other ostensibly similar wrappers. This PR rewrites the doc to match current formatting standards and offer more guidance on usage.

I don't think the fixed-width demo does a great job of demonstrating its usage (as I understand it anyway), so I need to revise it before this will be ready for review.

[mui-bot]

Netlify deploy preview

• docs/data/material/components/container/container.md
• docs/data/system/components/container/container.md

Bundle size report

No bundle size changes (Toolpad) No bundle size changes

Generated by :no_entry_sign: dangerJS against 63bbe20f43f196ad0656a7c4c873741d6351f3c7