Add and use new Signals struct (#13314)

# Description
This PR introduces a new `Signals` struct to replace our adhoc passing
around of `ctrlc: Option<Arc<AtomicBool>>`. Doing so has a few benefits:
- We can better enforce when/where resetting or triggering an interrupt
is allowed.
- Consolidates `nu_utils::ctrl_c::was_pressed` and other ad-hoc
re-implementations into a single place: `Signals::check`.
- This allows us to add other types of signals later if we want. E.g.,
exiting or suspension.
- Similarly, we can more easily change the underlying implementation if
we need to in the future.
- Places that used to have a `ctrlc` of `None` now use
`Signals::empty()`, so we can double check these usages for correctness
in the future.

crates/nu-protocol/src/errors/shell_error.rs

@@ -1187,6 +1187,13 @@ pub enum ShellError {
         span: Option<Span>,
     },
 
+    /// Operation interrupted
+    #[error("Operation interrupted")]
+    Interrupted {
+        #[label("This operation was interrupted")]
+        span: Span,
+    },
+
     /// Operation interrupted by user
     #[error("Operation interrupted by user")]
     InterruptedByUser {