Re-think gradient application to base and stroke

Describe the problem

Right now, the Graphics Tools/Standard and Graphics Tools/Standard Canvas shaders apply base colors/gradients and strokes (border lights) using paradigms convenient to HoloLens 1 and 2 but are not very flexible.

Describe the solution you'd like

We should spend some time to reevaluate how base colors and stokes are selected/enabled/disabled. This will take some refactoring of the shader code and inspector. This might even be a good opportunity to add shader graph nodes for these effects.

Describe alternatives you've considered

Live with the existing workflow.

Additional context

See how stoke gradients are currently hidden in the UI:

Inizia individuando gli shader Graphics Tools/Standard e Graphics Tools/Standard Canvas, quindi esamina il loro codice shader e la relativa UI dell’inspector. Esamina come vengono selezionati e abilitati o disabilitati i colori di base, i gradienti e i tratti, inclusi i controlli del gradiente del tratto attualmente nascosti. Il lavoro è completato quando il workflow refactoring e il comportamento dell’inspector sono definiti e implementati, e quando è stata valutata ogni opportunità per un nodo shader graph.