Give an explanation for NO_LCP when content is all canvas/SVG

[brendankenny]

Another person ran into #11326: https://twitter.com/FredKSchott/status/1376606554061893633

But currently the error we give is "Something went wrong with recording the trace over your page load. Please run Lighthouse again. (NO_LCP)". In this case, running Lighthouse again will not produce a better result the second time.

I'm not sure if there's anything we can do for the null perf score as long as we require LCP and LCP is defined the way it is (w3c/element-timing#47, w3c/element-timing#56), but we can at least let the user know what's happening.

Hand waving the heuristics here, but if

• there's no LCP
• there is painted content
• all of that content is SVG or canvas

we should give a custom NO_LCP error to let them know the reason for the null score.

related: #11326