Officially deprecate lazy_static

[KodrAus]

lazy_static has served the community well over the better part of a decade. Over that time, the Rust language has evolved, and better alternatives built on that evolution have emerged. That functionality has now made its way into the standard library, with aspects of it stabilizing from 1.70.0.

This library hasn't seen steady maintainership in some time. To support migration off lazy_static and towards once_cell or the standard library's types I propose we formally deprecate this library.

cc @rust-lang-nursery/libs-contributors

[Fishrock123]

I think this library is still worth having, but with it's implementation switched to once_cell.

The interface of lazy_static is often much better for use cases where there isn't much worry of fallibility or misordering.

E.g. static regexes from string literals.