Improvement: replace lazy_static with once_cell

[darnuria]

Hello,

I would suggest to change lazy_static for once_cell, lazy static was needed because back in 2015 in rust 1.0 it was impossible to express something like a compile time shared global ressource but safely accessed.

Since 2019, it's possible with : https://github.com/matklad/once_cell also the author openned a RFC PR 0000-standard-lazy-types.md to make it in std Tracking Issue for once_cell

It's used here : https://github.com/Gandi/jbod-rs/blob/main/src/prometheus.rs#L54-L71 and maybe used for regex compiled on the fly.

Gains:

• Less macro code
• API in standardisation

[araujobsd]

as it is not a critical issue, I'm closing this issue! Please, feel free to submit a PR with the proper changes.