Bump to 1.65

[c410-f3r]

Replaces the num_cpus project with the built-in std::thread::available_parallelism() method to decrease the number of transient dependencies for downstream crates.

Bumping to 1.65 instead of 1.64 to allow the possible inner usage of let_else and GAT.

[Darksonn]

We are not bumping the MSRV just to use the let_else feature.

[c410-f3r]

???

The intend of this PR is to remove num_cpus. If let_else or any other language feature is not desired, then the MSRV can be set to 1.64.

[Darksonn]

You named the PR "bump to 1.65", so I assumed that this was the primary change.

@seanmonstar What is the status on the num-cpus crate?

[Darksonn]

then the MSRV can be set to 1.64.

Why does using available_parallelism require an msrv bump at all? As far as I can tell, it's available since 1.59.

[c410-f3r]

For Linux machines, 1.63 only makes use of cgroupv2 and such exclusive behavior led to issues like rust-lang/rust#97549.

In 1.64, cgroupv1 is also supported (rust-lang/rust#97925, https://releases.rs/docs/1.64.0/).

[Darksonn]

Okay. Can you open an issue to switch to available_parallelism instead of a PR? If we have to bump the msrv, then I'd like to time it together with the upgrade to mio v1.0.

[c410-f3r]

#6211

[Darksonn]

Can you add the information about the msrv requirement in the issue? Thank you!