Providers without metadata service or serverInfo shouldn't break dashboard (#1761)

- Fix a number of issues that arose while testing a provider without a metadata service or serverInfo object returned via DMP calls. These should be optional services/features and we should be resilient to them not existing. In most places we already have these checks
- This does not cover a number of "improvement" scenarios, such as filtering extension tabs by provider, and defaulting any tabs that don't specify a provider to be MSSQL. This and some other features to ensure things make sense will be implemented in separate PRs but this unblocked the scenario

src/sql/parts/dashboard/widgets/tasks/tasksWidget.component.ts

@@ -166,7 +166,6 @@ export class TasksWidget extends DashboardWidget implements IDashboardWidget, On
 	}
 
 	public runTask(task: ICommandAction) {
-		let serverInfo = this._bootstrap.connectionManagementService.connectionInfo.serverInfo;
 		this.commandService.executeCommand(task.id, this._profile);
 	}