Build with lto = "fat"

[cartercanedy]

I've noticed a significant increase in performance and reduction in binary size when compiling in release with fat lto enabled. It definitely hogs a bunch of memory, so it may not be feasible with the standard github runner's memory constraints, but it might be worth including as a separate build pipeline until it's for sure known to be stable.

[deevus]

Feel free to create a PR so that I can test it out.