Remove jQuery on the frontend

Summary

This is the final step to conclude this Epic PLANET-5663.

Requirements

• Dequeue jQuery from public assets (but leave it for admin)
• Potentially remove it also from package.json, since we enqueuing it from a CDN for admin assets.
• Test that blocks are not affected by this change.
• Test that admin code is not affected by this change (including Image Archive).
• Test that existing plugins are not affected by this or they are enqueuing their own version of jquery if needed.
• Before merging the final PR, decided on an EOL date to communicate with NROs. Some child themes may depend on jquery being there from the master- theme.