Inconsistent snapshots in test-e2e-release due to partially loaded scenes

[lukemckinstry]

What happened?

In the release process running npm run test-e2e-release produces false positive errors because elements in the scene are at slightly different states in the loading process.

Examples:

It appears the scene has not changed but snapshots were taken at slightly different states in the loading process.

More consistent criteria for taking snapshots could also reduce false positive errors in other cases, eg. animation, particle systems

Reproduction steps

...

Sandcastle example

No response

Environment

Browser:
CesiumJS Version:
Operating System:

[ggetz]

Thanks @lukemckinstry! Some of this may have been introduced by the change in #12226.

We'll want to ensure:

1. The examples are each set to a consistent time. CesiumJS uses the current system time by default, which can result in different lighting and simulation conditions
2. We properly wait for network requests to settle (such as with waitForLoadState("networkidle") or a better handler if we can find one) at the right time
3. We advance system time such that promises can resolve and animations run in a deterministic way