refactor: ensure range is bounded (#15429)

No linked issue, it's a follow-up of 2 PRs I recently made to improve
some math commands. (#15319)

# Description
Small refactor to simplify the code. It was suggested in the comments of
my previous PR.

# User-Facing Changes
None

# Tests + Formatting
Tests, fmt and clippy OK

# After Submitting
Nothing more required

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

@@ -1,6 +1,7 @@
 //! A Range is an iterator over integers or floats.
 
 use crate::{ast::RangeInclusion, ShellError, Signals, Span, Value};
+use core::ops::Bound;
 use serde::{Deserialize, Serialize};
 use std::{cmp::Ordering, fmt::Display};
 
@@ -631,6 +632,13 @@ impl Range {
         }
     }
 
+    pub fn is_bounded(&self) -> bool {
+        match self {
+            Range::IntRange(range) => range.end() != Bound::<i64>::Unbounded,
+            Range::FloatRange(range) => range.end() != Bound::<f64>::Unbounded,
+        }
+    }
+
     pub fn into_range_iter(self, span: Span, signals: Signals) -> Iter {
         match self {
             Range::IntRange(range) => Iter::IntIter(range.into_range_iter(signals), span),