Simplify SIGQUIT handling (#11381)

# Description
Simplifies `SIGQUIT` protection to a single `signal` ignore system call.

# User-Facing Changes
`SIGQUIT` is no longer blocked if nushell is in non-interactive mode
(signals should not be blocked in non-interactive mode).
Also a breaking API change for `nu_protocol`.

# Tests + Formatting
Should come after #11178 for testing.

crates/nu-cli/src/repl.rs

@@ -213,20 +213,6 @@ pub fn evaluate_repl(
             use_color,
         );
 
-        start_time = std::time::Instant::now();
-        // Reset the SIGQUIT handler
-        if let Some(sig_quit) = engine_state.get_sig_quit() {
-            sig_quit.store(false, Ordering::SeqCst);
-        }
-        perf(
-            "reset sig_quit",
-            start_time,
-            file!(),
-            line!(),
-            column!(),
-            use_color,
-        );
-
         start_time = std::time::Instant::now();
         let config = engine_state.get_config();