Allow Progress padding to be customizable

[sandrofigo]

As already mentioned by this issue from another user #1346, it would be nice to have a way to control the automatically inserted paddings above and below the rendered progress content.

I was thinking about adding an extension method in ProgressExtensions to modify the vertical padding that is then used in DefaultProgressRenderer:

spectre.console/src/Spectre.Console/Live/Progress/Renderers/DefaultProgressRenderer.cs

Line 113 in b21e07e

_live.SetRenderable(new Padder(_renderHook(layout, tasks), new Padding(0, 1)));

Example:

AnsiConsole.Progress()
    .Padding(0)   // Adjust top and bottom padding
    .Start(ctx =>
    {
        // Omitted
    });

Similarly an extension method could be added for Status in StatusExtensions.

What do you think?