Update to windows-sys 0.61

[hanna-kruppe]

Tokio and mio already updated to windows-sys 0.61, so socket2 requiring 0.60 makes it hard to avoid multiple copies of windows-sys. In addition, 0.61 finally drops the dependency on large pre-built import libraries (from windows-targets) in favor of Rust's raw-dylib feature.

Since no code changes are needed, I relaxed the version requirement (still allowing 0.60) to avoid increasing socket2's MSRV.

[hanna-kruppe]

FWIW, the MSRV bump would be 1.70 -> 1.71. It seems that CI doesn't exercise the windows + Rust 1.70 combination, but it would give this error:

error: package `windows-link v0.2.1` cannot be built because it requires rustc 1.71 or newer, while the currently active rustc version is 1.70.0
Either upgrade to rustc 1.71 or newer, or use
cargo update -p [email protected] --precise ver
where `ver` is the latest version of `windows-link` supporting rustc 1.70.0

which unfortunately makes the wrong suggestion, the fix is to run

cargo update windows-sys --precise 0.60.2

[Thomasdezeeuw]

We're not going to increase the MSRV in v0.6. I also don't see a new (v0.7/v1) release in the near future as we just released v0.6 and I don't want to create churn for windows-sys.

We though we finally fixed all the windows-sys related churn, but not yet :(

[hanna-kruppe]

This PR doesn't increase MSRV, though. It would make it more annoying to use socket2 on Rust 1.70, since cargo's MSRV-aware resolver doesn't always generate a lockfile that works, but using 1.70 would remain entirely possible.

[hanna-kruppe]

FWIW, many other popular crates with MSRV < 1.71 also depend on windows-sys with multi-version ranges that allow but don't require windows-sys 0.61. Among the top 20 reverse dependencies:

crate	MSRV	windows-sys range
rustix	1.63	0.52 -- 0.61
tempfile	1.63	0.52 -- 0.61
errno	1.56	0.52 -- 0.61
anstyle-query	1.66.0	0.60 -- 0.61
nu-ansi-term	1.62.1	0.59 -- 0.61
is-terminal	1.63.0	0.52 -- 0.61

(disclaimer: the anstyle-query version range was merged and released just yesterday, on my request)

So what this PR is proposing is a common practice, and anyone who needs MSRV <= 1.70 for Windows builds is probably already used to dealing with the cargo update --precise dance.