Crate vendoring hangs indefinitely upon proxy issues

[felixmulder]

Hi!

We (Stripe) noticed that when vendoring crates cargo-bazel will hang forever in:

rules_rust/crate_universe/src/metadata.rs

Lines 224 to 239 in 608af09

	let output = self
	.cargo_bin
	.command()?
	// Cargo detects config files based on `pwd` when running so
	// to ensure user provided Cargo config files are used, it's
	// critical to set the working directory to the manifest dir.
	.current_dir(manifest_dir.as_std_path())
	.arg("fetch")
	.arg("--manifest-path")
	.arg(manifest_path.as_std_path())
	.arg("--verbose")
	.output()
	.context(format!(
	"Error running cargo to fetch crates '{}'",
	manifest_path
	))?;

due to the cargo commands not being configured with timeouts. Low-hanging fruit here would be setting some default timeouts here that make sense ☺️

Thanks for an awesome ruleset!

// F