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-explore/src/lib.rs

@@ -11,7 +11,7 @@ use commands::{ExpandCmd, HelpCmd, NuCmd, QuitCmd, TableCmd, TryCmd};
 pub use default_context::add_explore_context;
 pub use explore::Explore;
 use explore::ExploreConfig;
-use nu_common::{collect_pipeline, has_simple_value, CtrlC};
+use nu_common::{collect_pipeline, has_simple_value};
 use nu_protocol::{
     engine::{EngineState, Stack},
     PipelineData, Value,
@@ -28,7 +28,6 @@ mod util {
 fn run_pager(
     engine_state: &EngineState,
     stack: &mut Stack,
-    ctrlc: CtrlC,
     input: PipelineData,
     config: PagerConfig,
 ) -> Result<Option<Value>> {
@@ -45,14 +44,14 @@ fn run_pager(
         p.show_message("For help type :help");
 
         let view = binary_view(input, config.explore_config)?;
-        return p.run(engine_state, stack, ctrlc, Some(view), commands);
+        return p.run(engine_state, stack, Some(view), commands);
     }
 
     let (columns, data) = collect_pipeline(input)?;
 
     let has_no_input = columns.is_empty() && data.is_empty();
     if has_no_input {
-        return p.run(engine_state, stack, ctrlc, help_view(), commands);
+        return p.run(engine_state, stack, help_view(), commands);
     }
 
     p.show_message("For help type :help");
@@ -60,11 +59,11 @@ fn run_pager(
     if let Some(value) = has_simple_value(&data) {
         let text = value.to_abbreviated_string(config.nu_config);
         let view = Some(Page::new(Preview::new(&text), false));
-        return p.run(engine_state, stack, ctrlc, view, commands);
+        return p.run(engine_state, stack, view, commands);
     }
 
     let view = create_record_view(columns, data, is_record, config);
-    p.run(engine_state, stack, ctrlc, view, commands)
+    p.run(engine_state, stack, view, commands)
 }
 
 fn create_record_view(