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

[iorizu]

Exactly what is says on the tin.

We can't replace once_cell::OnceCell with std::cell::OnceCell yet because expect-test uses the try api (rust-lang/rust#109737).

[iorizu]

The CI failure is caused by a strange cfg value defined in the cmd! macro. That macro is imported from xshell 0.1.17 via xaction 0.2.4. The latest version of xshell doesn't have this issue, but the repo of xactions is archived so it can't be fixed.

I think the two options are:

• Remove the dependency on xactions or
• Add a dependency on a later version of xshell and import cmd! from there

I'd rather remove the dep on xactions.