feat: relax block_on top level function to accept IntoFuture

[tisonkun]

This would increase the MSRV to 1.64.0.

I don't know what is the MSRV of this project now and how can I find it.

cc @zesterer

[zesterer]

Thanks! I've not actually decided on a hard policy yet, and have just avoided anything that would have needed an MSRV nudge.

Something I'm considering is an '18 months' policy, which would require us to compile on 1.69. This is no accident: 1.68 introduced the pin! macro, which would permit us to remove the only unsafe code in the crate. What do you think about this?

[tisonkun]

What do you think about this?

1. It's reasonable to bump to 1.69.
2. It would be nice to add MSRV meta info at:

• README, e.g., https://github.com/fast/logforth?tab=readme-ov-file#supported-rust-versions-msrv-175
• Cargo.toml, e.g., https://github.com/fast/logforth/blob/f8cfddd8ed9f286f2efdfb289e9c29527ca31636/Cargo.toml#L24
• Ensure in CI, e.g., https://github.com/fast/logforth/blob/f8cfddd8ed9f286f2efdfb289e9c29527ca31636/.github/workflows/ci.yml#L61-L72

Hopefully these help.

[tisonkun]

For policy, here is a reference: https://github.com/tisonkun/cronexpr?tab=readme-ov-file#minimum-rust-version-policy