Optimized rendering for image traces

[nicolaskruchten]

Breaking this off of #4301

Let's carefully think about whether or not this would be a breaking change and if we need a new attribute, but clearly this is needed, as right now we're avoiding using image traces in favour of layout.image for performance reasons.

Note that this rendering concern is distinct from the input specification in base64-encoded PNG or via URL, which will be tracked in #4841

cc @emmanuelle @nicholas-esterer

[nicolaskruchten]

In principle, this should address #4377 on supported browsers, right @antoinerg ?

also cc @jonmmease

[antoinerg]

In principle, this should address #4377 on supported browsers, right @antoinerg ?

also cc @jonmmease

It should definitely get rid of the flashing but it probably won't help with the tooltip issue (#4570).

[archmoj]

Could we close this issue now that #5075 merged?