Switch from serde_yaml to serde_yml (#14630)

# Description
This PR fixes #14339.

Since [serde_yaml](https://docs.rs/serde_yaml/latest/serde_yaml/) is
already deprecated, replaced it with
[serde_yml](https://doc.serdeyml.com/serde_yml/).

After this change, the `to yaml` boolean parsing issue in #14339 is also
fixed.
Now the command
```
['y' 'Y' 'yes' 'Yes' 'YES' 'n' 'N' 'no' 'No' 'No' 'on' 'On' 'ON' 'off' 'Off' 'OFF'] | to yaml
```
will return
```
- 'y'
- 'Y'
- 'yes'
- 'Yes'
- 'YES'
- 'n'
- 'N'
- 'no'
- 'No'
- 'No'
- 'on'
- 'On'
- 'ON'
- 'off'
- 'Off'
- 'OFF'
```

# User-Facing Changes

I'm not sure if the yaml spec change is a user-facing change.

crates/nu-command/tests/format_conversions/yaml.rs

@@ -48,3 +48,18 @@ fn convert_dict_to_yaml_with_integer_floats_key() {
     assert!(actual.out.contains("2.11"));
     assert!(actual.err.is_empty());
 }
+
+#[test]
+fn convert_bool_to_yaml_in_yaml_spec_1_2() {
+    let actual = nu!(pipeline(
+        r#"
+            [y n no On OFF True true false] | to yaml
+        "#
+    ));
+
+    assert_eq!(
+        actual.out,
+        "- 'y'- 'n'- 'no'- 'On'- 'OFF'- 'True'- true- false"
+    );
+    assert!(actual.err.is_empty());
+}