Apply nightly clippy lints (#9654)

# Description
- A new one is the removal of unnecessary `#` in raw strings without `"`
inside.
-
https://rust-lang.github.io/rust-clippy/master/index.html#/needless_raw_string_hashes
- The automatically applied removal of `.into_iter()` touched several
places where #9648 will change to the use of the record API. If
necessary I can remove them @IanManske to avoid churn with this PR.
- Manually applied `.try_fold` in two places
- Removed a dead `if`
- Manual: Combat rightward-drift with early return

crates/nu-protocol/src/value/stream.rs

@@ -64,11 +64,7 @@ impl RawStream {
     pub fn chain(self, stream: RawStream) -> RawStream {
         RawStream {
             stream: Box::new(self.stream.chain(stream.stream)),
-            leftover: self
-                .leftover
-                .into_iter()
-                .chain(stream.leftover.into_iter())
-                .collect(),
+            leftover: self.leftover.into_iter().chain(stream.leftover).collect(),
             ctrlc: self.ctrlc,
             is_binary: self.is_binary,
             span: self.span,