Rename calc to math eval and allow it to optionally take an expression as an argument (#2195)

* Rename `calc` to `math eval` and allow it to optionally take the expression as an argument

* Moved calc tests to math eval
Also added 2 tests and changed 1 test

* Move calc docs to math eval

crates/nu-cli/tests/commands/math/eval.rs

@@ -0,0 +1,73 @@
+use nu_test_support::{nu, pipeline};
+
+#[test]
+fn evaluates_two_plus_two() {
+    let actual = nu!(
+        cwd: ".", pipeline(
+        r#"
+        math eval "2 + 2"
+        "#
+    ));
+
+    assert!(actual.out.contains("4.0"));
+}
+
+#[test]
+fn evaluates_two_to_the_power_four() {
+    let actual = nu!(
+        cwd: ".", pipeline(
+        r#"
+        echo "2 ^ 4" | math eval
+        "#
+    ));
+
+    assert!(actual.out.contains("16.0"));
+}
+
+#[test]
+fn evaluates_three_multiplied_by_five() {
+    let actual = nu!(
+        cwd: ".", pipeline(
+        r#"
+        echo "3 * 5" | math eval
+        "#
+    ));
+
+    assert!(actual.out.contains("15.0"));
+}
+
+#[test]
+fn evaluates_twenty_four_divided_by_two() {
+    let actual = nu!(
+        cwd: ".", pipeline(
+        r#"
+        echo "24 / 2" | math eval
+        "#
+    ));
+
+    assert!(actual.out.contains("12.0"));
+}
+
+#[test]
+fn evaluates_twenty_eight_minus_seven() {
+    let actual = nu!(
+        cwd: ".", pipeline(
+        r#"
+        echo "28 - 7" | math eval
+        "#
+    ));
+
+    assert!(actual.out.contains("21"));
+}
+
+#[test]
+fn evaluates_pi() {
+    let actual = nu!(
+        cwd: ".", pipeline(
+        r#"
+        math eval pi
+        "#
+    ));
+
+    assert!(actual.out.contains("3.14"));
+}

crates/nu-cli/tests/commands/math/mod.rs

@@ -1,5 +1,7 @@
 mod avg;
+mod eval;
 mod median;
+mod sum;
 
 use nu_test_support::{nu, pipeline};