Refs: #42470, #34625, #43307

• macOS @mjbvz
• Linux @aeschli
• Windows @alexandrudima

Complexity: 3

The drag and drop support in the workbench was cleaned up to allow for more DND scenarios.

The list of drag sources include:

• files and folders from the files explorer
• an editor from the open editors view
• search result file
• problem entry on a file
• an editor tab
• file(s) from the desktop

The list of drop targets include:

• the files explorer
• the open editors view
• an editor tab
• the editor area

Play around with dragging from the sources to the targets and verify the behaviour makes sense to you. Check the scenarios outlined in the release notes are working well: https://github.com/Microsoft/vscode-docs/blob/vnext/release-notes/v1_21.md#better-drag-and-drop-support