Next-generation `gen_resources`

[etpinard]

Mostly cherry-picking from https://github.com/plotly/Dash.jl/pull/208, this PR updates the 18+ months old artifacts with resources from dash v2.10.2.

The updated tarball is hosted on: https://github.com/plotly/DashCoreResources/releases/tag/v2.10.2%2B0

We had to make two modifications to our tests to make them pass with the new resources:

• commit 408138fffb078e60f0ea89dea28c2e085763babe adapts the Promise in clientside callback test as now JS Promises do work inside clientside callbacks thanks to dash#2009, released in dash v2.4.0
• commit 5cc67c39501291c5ef4482b9dedf87b36b2b849b adapts the devtools prop check test suite (essential what this piece of a very large patch did in python) now that nested props are valid since dash#1763, released in dash v2.1.0

and we also had to update two percy baselines to account for CSS changes.

I hope the instructions added in ff135bd57b9cb328efee37abba2cd1a26a874af1 will make this process accessible to other Dash.jl contributors in the future.

[etpinard]

I've been personally using the updated v2.10.2 artifacts for about a week now without issues.

So, I'll merge this branch into dev and let it sit there so that other Dash.jl developers can try the new artifacts out using

pkg> add Dash#dev

I'm planning on releasing the new artifacts as part of Dash.jl@v1.3.0 1-2 weeks from now, right before JuliaCon 2023.