Port fetch (with fixes) (#660)

* Port fetch to engine-q

* Fix check for path as a string

* Add a timeout flag and fix some span issues

* Add a temporary fetch command that returns byte streams. Got rid of async stuff as we're using the blocking feature of tokio

* More tweaks for the bytestream

* Rewrite fetch using ByteStreams

* buffer read on bytes directly

Co-authored-by: Stefan Stanciulescu <contact@stefanstanciulescu.com>

crates/nu-protocol/src/shell_error.rs

@@ -152,6 +152,10 @@ pub enum ShellError {
     #[diagnostic(code(nu::shell::unsupported_input), url(docsrs))]
     UnsupportedInput(String, #[label("{0}")] Span),
 
+    #[error("Network failure")]
+    #[diagnostic(code(nu::shell::network_failure), url(docsrs))]
+    NetworkFailure(String, #[label("{0}")] Span),
+
     #[error("Command not found")]
     #[diagnostic(code(nu::shell::command_not_found), url(docsrs))]
     CommandNotFound(#[label("command not found")] Span),