Improve Web IDE panels and workflows to support with previews, traces, terminal and commits

By GitLab %11.0 we will have markdown previews, CI traces, Git commits and maybe a web terminal. The current panels and workflows won't scale to support this. We should start to immediately make improvements to existing interfaces and have a plan for how the workflow will eventually work.

Proposal

• Design workflow that will support viewing source, traces, and terminal simultaneously
• Review workflow for committing changes while traces and terminal are visible
• Consider splitting commit workflow into distinct area

Design

Most of the design is already in. This design now mostly defines how to display the secondary information right sidebar!

• Reusing header design of the left and also boldened so we align it with other headers throughout the interface (also updated left sidebar headers)