I've been working on streaming and pipeline interruption lately. It was
bothering me that checking ctrl+c (something we want to do often) always
requires a bunch of boilerplate like:
```rust
use std::sync::atomic::Ordering;
if let Some(ctrlc) = &engine_state.ctrlc {
if ctrlc.load(Ordering::SeqCst) {
...
```
I added a helper method to cut that down to:
```rust
if nu_utils::ctrl_c::was_pressed(&engine_state.ctrlc) {
...
```
e215fbbd08