Process GeneratedEnvironmentMapLight on-demand

[dylansechet]

Objective

GeneratedEnvironmentMapLight currently does work every frame converting a cubemap into an environment map, which can be performance heavy (#24517). This PR makes this conversion happen on demand instead.

This addresses the first item in #20212.

Solution

GeneratedEnvironmentMapLight now exposes a regenerate boolean field, which is reset during extraction. This copies the behavior of TAA's reset field.

However, the boolean isn't quite enough: if the pipelines/assets aren't ready on the frame when regenerate is set to true, nothing runs and you end up with a black env map. To ensure we retry to process the env map until the filtering has actually run, I've created a render world component called RegenerateEnvironmentMap which only gets removed once the filtering has actually run.

Testing

• Ran the reflection_probes and atmosphere examples

On the reflection_probes example, current PR in yellow and main in red. This was run on a noisy laptop, so should probably be taken with a pinch of salt:

[IceSentry]

I generally like the solution, but I don't know if we should make this opt in, as in, always update by default. Or at least offer some automatic ways to update it.