bsn: throw error when using caching syntax on unsupported scene entries (#24473)

# Objective

Implement changes discussed with cart around erroring when using caching
syntax where its not implemented.


## Solution

Throw a compile error, in a way which is easy to remove once caching
exists/works for more cases.

Also contains a commit to alleviate trait errors which will (from my
experience writing this PR and fixing them in bevy) arise from fixing
this for existing bsn code. This commit can be dropped if not desired.
This would ideally be fixed upstream so this workaround can be removed:
https://github.com/rust-lang/rust/issues/141258#issuecomment-4565897810

Note: The error caused by this workaround is far from ideal. It
initially looks like a method call is missing, but ultimately the
hint/advice *is* correct
<img width="1982" height="477" alt="image"
src="https://github.com/user-attachments/assets/879f7630-ada8-4e63-9c59-80be466f37cf"
/>


## Testing

- `cargo test -p bevy_scene --lib`
- `cargo check`

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Co-authored-by: Carter Anderson <mcanders1@gmail.com>