Hidden & advanced widgets

[pythongosssss]

Adds support for hiding widgets and flagging them as advanced

firefox_KM9druzde6.webm

In this example i've made 2 random widgets advanced:

app.graph.nodes.find(n => n.type === "EmptyLatentImage").widgets[1].advanced = true;
app.graph.nodes.find(n => n.type === "KSampler").widgets[1].advanced = true;

Scanned through all the references to widgets so hopefully didn't miss anywhere that was using them for size calculations.

[webfiltered]

Nice! I did some minor refactors to match existing use (and future use for canvas): f53868f

[huchenlei]

Can we have some sort of visual indication that a widget is advanced?