Switch to the rgb crate v0.9 pixel types and trait.

[ripytide]

Although not actually released yet, when v0.9 is released it should have several Pixel traits that are just as powerful or more than the one used already in this crate. Similar to that from pixeli demonstrated in #2255.

It would also make this crate more interoperable with other image crates as the rgb pixel types are commonly used for interoperability.

This would be a breaking change so I'd suggest we implement it for v0.26 #2245. This may also conflict with #2239.

[kornelski]

Having interoperability with the image types would be awesome. The image crate already depends on the rgb crate via AVIF encoder.

I plan to use the semver trick to keep structs in rgb v0.8 and v0.9 compatible. The v0.9 has an option to add a cleaned-up Pixel trait and other traits, to better align with the image crate.