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-plugin-test-support/src/lib.rs

@@ -8,8 +8,8 @@
 //! use nu_plugin::*;
 //! use nu_plugin_test_support::PluginTest;
 //! use nu_protocol::{
-//!     Example, IntoInterruptiblePipelineData, LabeledError, PipelineData, ShellError, Signature,
-//!     Span, Type, Value,
+//!     Example, IntoInterruptiblePipelineData, LabeledError, PipelineData, ShellError, Signals,
+//!     Signature, Span, Type, Value,
 //! };
 //!
 //! struct LowercasePlugin;
@@ -60,7 +60,7 @@
 //!                     // Errors in a stream should be returned as values.
 //!                     .unwrap_or_else(|err| Value::error(err, span))
 //!             },
-//!             None,
+//!             &Signals::empty(),
 //!         )?)
 //!     }
 //! }
@@ -83,7 +83,7 @@
 //!
 //! // #[test]
 //! fn test_lowercase() -> Result<(), ShellError> {
-//!     let input = vec![Value::test_string("FooBar")].into_pipeline_data(Span::test_data(), None);
+//!     let input = vec![Value::test_string("FooBar")].into_pipeline_data(Span::test_data(), Signals::empty());
 //!     let output = PluginTest::new("lowercase", LowercasePlugin.into())?
 //!         .eval_with("lowercase", input)?
 //!         .into_value(Span::test_data())?;

crates/nu-plugin-test-support/src/plugin_test.rs

@@ -11,7 +11,7 @@ use nu_protocol::{
     debugger::WithoutDebug,
     engine::{EngineState, Stack, StateWorkingSet},
     report_error_new, CustomValue, Example, IntoSpanned as _, LabeledError, PipelineData,
-    ShellError, Span, Value,
+    ShellError, Signals, Span, Value,
 };
 
 use crate::{diff::diff_by_line, fake_register::fake_register};
@@ -85,13 +85,13 @@ impl PluginTest {
     ///
     /// ```rust,no_run
     /// # use nu_plugin_test_support::PluginTest;
-    /// # use nu_protocol::{ShellError, Span, Value, IntoInterruptiblePipelineData};
+    /// # use nu_protocol::{IntoInterruptiblePipelineData, ShellError, Signals, Span, Value};
     /// # use nu_plugin::*;
     /// # fn test(MyPlugin: impl Plugin + Send + 'static) -> Result<(), ShellError> {
     /// let result = PluginTest::new("my_plugin", MyPlugin.into())?
     ///     .eval_with(
     ///         "my-command",
-    ///         vec![Value::test_int(42)].into_pipeline_data(Span::test_data(), None)
+    ///         vec![Value::test_int(42)].into_pipeline_data(Span::test_data(), Signals::empty())
     ///     )?
     ///     .into_value(Span::test_data())?;
     /// assert_eq!(Value::test_string("42"), result);
@@ -151,7 +151,7 @@ impl PluginTest {
                         Err(err) => Value::error(err, value.span()),
                     }
                 },
-                None,
+                &Signals::empty(),
             )?
         };
 
@@ -171,7 +171,7 @@ impl PluginTest {
                         Err(err) => Value::error(err, value.span()),
                     }
                 },
-                None,
+                &Signals::empty(),
             )
         }
     }

crates/nu-plugin-test-support/tests/lowercase/mod.rs

@@ -1,8 +1,8 @@
 use nu_plugin::*;
 use nu_plugin_test_support::PluginTest;
 use nu_protocol::{
-    Example, IntoInterruptiblePipelineData, LabeledError, PipelineData, ShellError, Signature,
-    Span, Type, Value,
+    Example, IntoInterruptiblePipelineData, LabeledError, PipelineData, ShellError, Signals,
+    Signature, Span, Type, Value,
 };
 
 struct LowercasePlugin;
@@ -53,7 +53,7 @@ impl PluginCommand for Lowercase {
                     // Errors in a stream should be returned as values.
                     .unwrap_or_else(|err| Value::error(err, span))
             },
-            None,
+            &Signals::empty(),
         )?)
     }
 }
@@ -72,7 +72,8 @@ impl Plugin for LowercasePlugin {
 fn test_lowercase_using_eval_with() -> Result<(), ShellError> {
     let result = PluginTest::new("lowercase", LowercasePlugin.into())?.eval_with(
         "lowercase",
-        vec![Value::test_string("HeLlO wOrLd")].into_pipeline_data(Span::test_data(), None),
+        vec![Value::test_string("HeLlO wOrLd")]
+            .into_pipeline_data(Span::test_data(), Signals::empty()),
     )?;
 
     assert_eq!(