Make HTTP requests cancellable when trying to connect (#8591)

Closes #8585.

Prior to this change, the `http` commands could get stuck for 30s while
attempting to make a connection to a remote server. After this change,
`ctrl+c` works as expected:


![image](https://user-images.githubusercontent.com/26268125/227395505-c2d5b19d-6228-4eac-836f-c0c3426b0c19.png)

To make this work, we perform blocking `ureq` calls in a background
thread and poll the channel while checking `ctrl+c`.

crates/nu-protocol/src/shell_error.rs

@@ -1056,6 +1056,13 @@ pub enum ShellError {
         #[label("Could not access '{column_name}' on this record")]
         span: Span,
     },
+
+    /// Operation interrupted by user
+    #[error("Operation interrupted by user")]
+    InterruptedByUser {
+        #[label("This operation was interrupted")]
+        span: Option<Span>,
+    },
 }
 
 impl From<std::io::Error> for ShellError {