Handle mixed LF+CRLF in lines (#7316)

This closes #4989. Previously `lines` was unable to handle text input
with CRLF line breaks _and_ LF line breaks.

### Before:

![image](https://user-images.githubusercontent.com/26268125/205207685-b25da9e1-19fa-4abb-8ab2-0dd216c63fc0.png)

### After:


![image](https://user-images.githubusercontent.com/26268125/205207808-9f687242-a8c2-4b79-a12c-38b0583d8d52.png)

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

@@ -48,3 +48,16 @@ fn lines_multi_value_split() {
 
     assert_eq!(actual.out, "6");
 }
+
+/// test whether this handles CRLF and LF in the same input
+#[test]
+fn lines_mixed_line_endings() {
+    let actual = nu!(
+        cwd: "tests/fixtures/formats", pipeline(
+        r#"
+            "foo\nbar\r\nquux" | lines | length
+        "#
+    ));
+
+    assert_eq!(actual.out, "3");
+}