.NET: Enable tools for workflows

There may be some scenarios where you want to provide a same set of tools to all agents participating in a workflow. It would be nice in a Workflow to be able to specify the array of tools there rather than separately per agent.

Something like `WithTools`:

```csharp
Workflow workflow = AgentWorkflowBuilder
.BuildSequential(writer, editor);
.WithTools(
[
AIFunctionFactory.Create(tools.GetAuthor),
AIFunctionFactory.Create(tools.GetTitle),
AIFunctionFactory.Create(tools.FormatStory)
]);
```