Pipeline sink refactor (#1359)

* Refactor pipeline ahead of block changes. Add '-c' commandline option

* Update pipelining an error value

* Fmt

* Clippy

* Add stdin redirect for -c flag

* Add stdin redirect for -c flag

crates/nu-parser/src/hir.rs

@@ -204,6 +204,12 @@ pub struct SpannedExpression {
     pub span: Span,
 }
 
+impl SpannedExpression {
+    pub fn new(expr: Expression, span: Span) -> SpannedExpression {
+        SpannedExpression { expr, span }
+    }
+}
+
 impl std::ops::Deref for SpannedExpression {
     type Target = Expression;