Remove runtime cost of Lazy() calls with alternative pattern

[jalberse]

There's a few places, namely in colorspace and spectra conversions, where Lazy is used to read and initialize large data tables. But, each call to access that data during runtime incurs a check on if that data is initialized.

I had tried to use const functions to initialize the constants, but we want to initialize with some more complex dependent functions that aren't const themselves.

https://dev.to/rustyoctopus/generating-static-arrays-during-compile-time-in-rust-10d8

This article has some good discussion on this topic.

I think we might want to generate these constants via a build.rs script.

[jalberse]

I'm not overly concerned about this - this doesn't seem to be somewhere we spend a lot of time in rendering from profiling. Low priority. Might even not do this; lazy initialization might just be more ergonomic than any initialization logic.

[jalberse]

I don't think this is actually something we want to do. I don't think it impacts performance, it's not in any hot loops I've seen. If it ever becomes an issue we can do it.