feat(tree-explorer): add delete document context menu item VSCODE-349

[Anemy]

VSCODE-349

This adds a setting confirmDeleteDocument which defaults true to show a confirmation when deleting a document. Can add more tests if folks would like that.

Delete.doc.from.tree.view.mp4

[alenakhineika]

Would it make sense to have this setting not only for deleting documents but for any deleting operation? I am wondering how often users expect a different confirmation behaviour for different entities.

[Anemy]

@alenakhineika good question, I was thinking that having this setting only for deleting documents makes sense as its most likely something that folks do more often in their development. I don't see dropping a database or collection happening often enough to warrant sharing a setting or having separate settings for each. Are there other delete behaviors you were thinking of?