Support "editor/title/run" toolbar commands

[DanTup]

VS Code added a new contribution for editor toolbar icons: "editor/title/run" and encouraged extensions to move their Run/Debug icons to them:

microsoft/vscode@97c7d2a

https://code.visualstudio.com/updates/v1_54#_limits-for-editor-title-menu-and-run-submenu:~:text=added%20the%20editor%2Ftitle%2Frun%20submenu

As a consequence, these buttons have disappeared from Theia, as it doesn't read commands from there.

Pushing them onto the front of editor/title commands may be an easy fix to support them, though VS Code goes a little further and collapses them into a single button with a drop-down menu:

Example definition: https://github.com/Dart-Code/Dart-Code/blob/393763bc887dce42953646e3ea7381060beefd93/package.json#L1059-L1071

[Tpuljak]

Would very much love to see this implemented. Extensions like Code Runner greatly improve UX using the run menu.