[workload] add maui-linux-gtk or maui-gtk to speed maui+self draw solution adoption on cross desktop platform development

### Description

I'd like to propose a maui workload to easy self draw cross-desktop solution, which seems very promise and easy community involve, as pointed by https://github.com/dotnet/Microsoft.Maui.Graphics.Controls/issues/57

the hardest part of the solution may be the maui Dotnet config part, like props, target, and workload, hope Maui upstream can do this work for the community.

After the work is done, evolution can drive by the community, which is easy and fast!

### Public API Changes

n.a

### Intended Use-Case

cross-desktop development

Start by reviewing the linked Microsoft.Maui.Graphics.Controls issue and the MAUI workload configuration for props, targets, and workload definitions. Determine the required maui-linux-gtk or maui-gtk scope and how cross-desktop self-draw development should be enabled. Done means the workload is supported and documented for the intended cross-desktop use case.

Written by the indexing model from the issue text.