web: Reload with canvas when webglcontextlost and 8+ instances exist

[danielhjacobs]

Intended to fix this comment in #1905 (comment)

[danielhjacobs]

I suppose technically, if the situation exists where the browser supports the webgl renderer but not the canvas renderer, this may infinitely loop in a way. Since preferredRenderer doesn't force the renderer so the load may fallback to webgl.

Not sure how to address that, as forcedRenderer was not added (#10835) and neither was enableFallbackRenderers (#10900).

That said, I may be inventing a situation that will never occur. I can't think of why canvas would fail while webgl succeeds.

[danielhjacobs]

Addressed my comment by making is so calling reloadWithCanvasRenderer() when the preferredRenderer is already "canvas" will panic. I also made that function protected, since it shouldn't be used by end-users (the renderers are subject to change, and an end-user can just call load with a different preferredRenderer in their own config).