Use Iterator::intersperse in -e argument parsing when Rust 1.64.0 is released

[lopopolo]

This code manually joins a bunch of -e flags together:

artichoke/src/ruby.rs

Lines 166 to 175 in 9f2d43c

	let mut commands = commands.into_iter();
	let mut buf = if let Some(command) = commands.next() {
	command
	} else {
	return Ok(Ok(()));
	};
	for command in commands {
	buf.push("\n");
	buf.push(command);
	}

Iterator::intersperse will be stabilized in rust-lang/rust#99093. Combined with rust-lang/rust#82121, the code will be able to be rewritten to something like:

let buf = commands
    .into_iter()
    .map(Cow::Owned)
    .intersperse(Cow::Borrowed(OsStr::new("\n"))
    .collect::<OsString>();

[lopopolo]

It looks like the stabilization PR for Iterator::intersperse has been reverted.