Add the ability to detect when running remotely

See #1738.

src/shared/vscode/utils.ts

@@ -1,6 +1,12 @@
-import { commands, Uri } from "vscode";
+import { commands, ExtensionKind, extensions, Uri } from "vscode";
+import { dartCodeExtensionIdentifier } from "../constants";
 import { forceWindowsDriveLetterToUppercase } from "../utils";
 
+const dartExtension = extensions.getExtension(dartCodeExtensionIdentifier);
+// The extension kind is declared as Workspace, but VS Code will return UI in the
+// case that there is no remote extension host.
+export const isRunningLocally = dartExtension.extensionKind === ExtensionKind.UI;
+
 export function fsPath(uri: Uri | string) {
 	// tslint:disable-next-line:disallow-fspath
 	return forceWindowsDriveLetterToUppercase(uri instanceof Uri ? uri.fsPath : uri);