Fix: Put back Defaulting of EnvironmentMapUniform

[kfc35]

Objective

• I think this is the last fix associated with view bindgroup layout changes can cause crash #24084

Solution

• Some defaulting logic of EnvironmentMapUniform was removed — this just puts it back. It seems like it is critical to the rendering the desired mirror-y effects of the light_probe_blending and pcss examples, and it resolves the rendering strobing that happens for the affected examples.
• I do realize that this probably makes the ENVIRONMENTAL_MAP flag useless? Since every camera will then have an EnvironmentalMap. I might do that later (have to sleep!)

Alternative solution: add EnvironmentalMapLight to the examples’ cameras, but I am second guessing that based on the pre-existing function doc comment. It might be a usability thing to not have to include the EnvironmentalMapLight component… albeit I haven’t asked anyone about it.

This is in draft until I make up my mind about modifying the examples and changing user expectations vs putting back in the defaulting behavior. I do like how the feature gating ensures that we use one less uniform buffer...

Testing

• cargo run --example light_probe_blending --features="free_camera https” looks correct again
• cargo run --example pcss also looks correct again

[beicause]

See #24095