Use std::sync::OnceLock instead of once_cell::sync::Lazy

[rmg-x]

This PR removes the once_cell dependency and uses the std struct instead.
MSRV would go up to 1.70

See:

• https://doc.rust-lang.org/std/sync/struct.OnceLock.html
• https://blog.rust-lang.org/2023/06/01/Rust-1.70.0.html#oncecell-and-oncelock

[algesten]

Hi @rmg-x, welcome to ureq!

I do agree it would be nice to do this, but at this point we can't bump the MSRV. We decided on a rather conservative version requirement since our users have that need. See this issue from just two weeks ago: #712 - this was due to trying to use let-else syntax.

[DanGould]

Second the msrv concern, other than just being simple and correct, the reason I use ureq is because it builds on my target msrv 1.63.0

[rmg-x]

I can understand the concerns (because who wants their project to break?) but personally think it's the wrong approach for this library.

Eventually there will be a point where the MSRV is bumped and users will complain. I think it makes more sense to put the onus on people requiring a lower version (e.g. fork or use an older ureq version)

Regardless, I appreciate the responses and will leave the PR open, feel free to close it.

[algesten]

Closing since we are moving to 3.x