Fix easy clippy lints from latest stable (#16053)

1.88.0 was released today, clippy now lints (machine-applicable)
against:
- format strings with empty braces that could be inlined
  - easy win
- `manual_abs_diff`
- returning of a stored result of the last expression.
  - this can be somewhat contentious but touched only a few places

crates/nu-cmd-lang/src/core_commands/describe.rs

@@ -296,7 +296,7 @@ fn run(
             } else {
                 let value = stream.into_value();
                 let base_description = value.get_type().to_string();
-                Value::string(format!("{} (stream)", base_description), head)
+                Value::string(format!("{base_description} (stream)"), head)
             }
         }
         PipelineData::Value(value, ..) => {

crates/nu-cmd-lang/src/core_commands/error_make.rs

@@ -229,7 +229,7 @@ fn make_other_error(value: &Value, throw_span: Option<Span>) -> ShellError {
             error: "invalid error format.".into(),
             msg: "`$.label.start` should be smaller than `$.label.end`".into(),
             span: Some(label_span),
-            help: Some(format!("{} > {}", span_start, span_end)),
+            help: Some(format!("{span_start} > {span_end}")),
             inner: vec![],
         };
     }

crates/nu-cmd-lang/src/example_support.rs

@@ -221,23 +221,23 @@ impl std::fmt::Debug for DebuggableValue<'_> {
     fn fmt(&self, f: &mut std::fmt::Formatter<'_>) -> std::fmt::Result {
         match self.0 {
             Value::Bool { val, .. } => {
-                write!(f, "{:?}", val)
+                write!(f, "{val:?}")
             }
             Value::Int { val, .. } => {
-                write!(f, "{:?}", val)
+                write!(f, "{val:?}")
             }
             Value::Float { val, .. } => {
-                write!(f, "{:?}f", val)
+                write!(f, "{val:?}f")
             }
             Value::Filesize { val, .. } => {
-                write!(f, "Filesize({:?})", val)
+                write!(f, "Filesize({val:?})")
             }
             Value::Duration { val, .. } => {
                 let duration = std::time::Duration::from_nanos(*val as u64);
-                write!(f, "Duration({:?})", duration)
+                write!(f, "Duration({duration:?})")
             }
             Value::Date { val, .. } => {
-                write!(f, "Date({:?})", val)
+                write!(f, "Date({val:?})")
             }
             Value::Range { val, .. } => match **val {
                 Range::IntRange(range) => match range.end() {
@@ -280,7 +280,7 @@ impl std::fmt::Debug for DebuggableValue<'_> {
                 },
             },
             Value::String { val, .. } | Value::Glob { val, .. } => {
-                write!(f, "{:?}", val)
+                write!(f, "{val:?}")
             }
             Value::Record { val, .. } => {
                 write!(f, "{{")?;
@@ -305,22 +305,22 @@ impl std::fmt::Debug for DebuggableValue<'_> {
                 write!(f, "]")
             }
             Value::Closure { val, .. } => {
-                write!(f, "Closure({:?})", val)
+                write!(f, "Closure({val:?})")
             }
             Value::Nothing { .. } => {
                 write!(f, "Nothing")
             }
             Value::Error { error, .. } => {
-                write!(f, "Error({:?})", error)
+                write!(f, "Error({error:?})")
             }
             Value::Binary { val, .. } => {
-                write!(f, "Binary({:?})", val)
+                write!(f, "Binary({val:?})")
             }
             Value::CellPath { val, .. } => {
                 write!(f, "CellPath({:?})", val.to_string())
             }
             Value::Custom { val, .. } => {
-                write!(f, "CustomValue({:?})", val)
+                write!(f, "CustomValue({val:?})")
             }
         }
     }