support arrays of color and colorscale for line and fillcolor of `plotly.graph_objects.Scatter`

Coming from plotly.py. Since this is about the plotly.graph_objects module, the issue is posted here.

Currently, only plotly.graph_objects.Scatter.marker, plotly.graph_objects.Scatter.marker.gradient and plotly.graph_objects.Scatter.marker.line supports assigning colors by arrays of color along with colorscale.

Could the same color-setting techniques be allowed for plotly.graph_objects.Scatter.line and plotly.graph_objects.Scatter.fillcolor as well?

p.s. Links to the current documentation:

1. The following supports arrays of color with colorscale:

• marker.color
• marker.gradient.color
• maker.line.color

2. The following doesn't support arrays of color with colorscale:

• line.color
• fillcolor

Inizia tracciando il modo in cui Scatter.marker, marker.gradient e marker.line accettano array di colori con una colorscale, quindi confronta la gestione di Scatter.line e fillcolor. Conferma il comportamento previsto nei link alla documentazione esistenti e aggiungi una copertura che dimostri che gli array funzionano per entrambe le proprietà senza compromettere i colori scalari.