make math sqrt const (#13487)

# Description

Just a quick PR to demonstrate one way to make commands const.
related to https://github.com/nushell/nushell/issues/13482

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crates/nu-command/src/math/sqrt.rs

@@ -29,6 +29,10 @@ impl Command for SubCommand {
         vec!["square", "root"]
     }
 
+    fn is_const(&self) -> bool {
+        true
+    }
+
     fn run(
         &self,
         engine_state: &EngineState,
@@ -44,6 +48,23 @@ impl Command for SubCommand {
         input.map(move |value| operate(value, head), engine_state.signals())
     }
 
+    fn run_const(
+        &self,
+        working_set: &StateWorkingSet,
+        call: &Call,
+        input: PipelineData,
+    ) -> Result<PipelineData, ShellError> {
+        let head = call.head;
+        // This doesn't match explicit nulls
+        if matches!(input, PipelineData::Empty) {
+            return Err(ShellError::PipelineEmpty { dst_span: head });
+        }
+        input.map(
+            move |value| operate(value, head),
+            working_set.permanent().signals(),
+        )
+    }
+
     fn examples(&self) -> Vec<Example> {
         vec![Example {
             description: "Compute the square root of each number in a list",