make the behaviours of last and first more consistent (#9582)

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# Description

- fixes #9567 

I have fixed everything mentioned in the issue, and made their help
messages more similar.

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# User-Facing Changes
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helps us keep track of breaking changes. -->

- Previously, `last` on binary data returned an integer. Now it returns
a binary
- Now, `[] | last` and `[] | first` are both errors.
- Now, `ls | table | first` and `ls | table | last` are both errors.

crates/nu-command/tests/commands/first.rs

@@ -79,6 +79,28 @@ fn gets_first_row_as_list_when_amount_given() {
     assert_eq!(actual.out, "list<int> (stream)");
 }
 
+#[test]
+fn gets_first_bytes() {
+    let actual = nu!(pipeline(
+        r#"
+            (0x[aa bb cc] | first 2) == 0x[aa bb]
+        "#
+    ));
+
+    assert_eq!(actual.out, "true");
+}
+
+#[test]
+fn gets_first_byte() {
+    let actual = nu!(pipeline(
+        r#"
+            0x[aa bb cc] | first
+        "#
+    ));
+
+    assert_eq!(actual.out, "170");
+}
+
 #[test]
 // covers a situation where `first` used to behave strangely on list<binary> input
 fn works_with_binary_list() {
@@ -98,3 +120,15 @@ fn errors_on_negative_rows() {
 
     assert!(actual.err.contains("use a positive value"));
 }
+
+#[test]
+fn errors_on_empty_list_when_no_rows_given() {
+    let actual = nu!(pipeline(
+        r#"
+            []
+            | first
+        "#
+    ));
+
+    assert!(actual.err.contains("index too large"));
+}

crates/nu-command/tests/commands/last.rs

@@ -79,6 +79,28 @@ fn gets_last_row_as_list_when_amount_given() {
     assert_eq!(actual.out, "list<int> (stream)");
 }
 
+#[test]
+fn gets_last_bytes() {
+    let actual = nu!(pipeline(
+        r#"
+            (0x[aa bb cc] | last 2) == 0x[bb cc]
+        "#
+    ));
+
+    assert_eq!(actual.out, "true");
+}
+
+#[test]
+fn gets_last_byte() {
+    let actual = nu!(pipeline(
+        r#"
+            0x[aa bb cc] | last
+        "#
+    ));
+
+    assert_eq!(actual.out, "204");
+}
+
 #[test]
 fn last_errors_on_negative_index() {
     let actual = nu!(pipeline(
@@ -97,3 +119,15 @@ fn fail_on_non_iterator() {
 
     assert!(actual.err.contains("only_supports_this_input_type"));
 }
+
+#[test]
+fn errors_on_empty_list_when_no_rows_given() {
+    let actual = nu!(pipeline(
+        r#"
+            []
+            | last
+        "#
+    ));
+
+    assert!(actual.err.contains("index too large"));
+}