Replace lazy_static with once_cell

[hinto-janai]

rust-lang-nursery/lazy-static.rs#214

once_cell can be faster (10~20%) in contentious retrieval as well, test examples here https://github.com/matklad/once_cell/tree/master/examples - although you'll have to swap in lazy_static and test yourself.

Once std::sync::LazyLock is stabilized, Lazy can be renamed and once_cell can be removed altogether. Tracking issue.

[kayabaNerve]

Thanks for the interest!

We currently have both lazy_static and once_cell in-tree due to ecosystem fragmentation. Accordingly, any edits here don't actually reduce the entire amount of dependencies in our dependency graph. Accordingly, this PR must be evaluated for what goal it works towards/immediate benefits.

We've prior replaced lazy_static with std options. Even though std's lazy isn't stabilized, its OnceLock is. It has a worse API, requiring a helper function be defined with it, yet it removes all non-std dependencies. While again, this doesn't apply to our entire tree (due to dependencies which haven't updated), it does at least move parts of our codebase to purging third party crates from their sub-trees for this purpose.

once_cell is another lazy_static. It may be a better lazy_static, yet that doesn't change it's another lazy_static. A 3rd party library for which 1st party alternatives now sort-of exist. While I do still lean towards merging this, as why not + slightly reduced compile times, I don't see such a clear-cut benefit compared to moving to OnceLock + helper function.

I'll merge once the CI passes 👍 Thanks for the interest, and the support. Let me know if you'd be interested in a follow up commit to replace once_cell with OnceLock.

[hinto-janai]

Let me know if you'd be interested in a follow up commit to replace once_cell with OnceLock

Sure - to be clear there are no instances of OnceLock in serai, do you mean you'll start using once_cell::Once from now on and those should be replaced in the future? If so, sure.

Although considering the dependency tree, lazy_static and once_cell will probably be used for the rest of time even if serai doesn't use them :)

[kayabaNerve]

coins/ does use OnceLock, as re-exported from std by std-shims when building for std platforms.

I can dream regarding achieving a minimal dependency tree :P

[kayabaNerve]

I think this should actually be written as ::new(env_logger::init), not ::new(|| env_logger::init()). clippy will likely complain otherwise.

[hinto-janai]

Sorry for all the pushes, I don't have librocksdb so can't test locally :)

The last push failed because clippy wanted the function item directly, it wanted ::new(env_logger::init) instead of ::new(|| env_logger::init()), I just forgot to get rid of the closure.

[kayabaNerve]

Thanks again. I'll also look at removing lazy_static from our substrate dependencies, as that should remove most consumers of lazy_static in our tree...