Include subsecond precision in stat atime/ctime

Previously only mtime supported this.  Follows on to
1d0dcb5962.  References #3233.
References s3fs-fuse/s3fs-fuse#2740.

src/uu/stat/src/stat.rs

@@ -1115,7 +1115,11 @@ impl Stater {
                     // time of last access, human-readable
                     'x' => OutputType::Str(pretty_time(meta, MetadataTimeField::Access)),
                     // time of last access, seconds since Epoch
-                    'X' => OutputType::Integer(meta.atime()),
+                    'X' => {
+                        let (sec, nsec) = metadata_get_time(meta, MetadataTimeField::Access)
+                            .map_or((0, 0), system_time_to_sec);
+                        OutputType::Float(sec as f64 + nsec as f64 / 1_000_000_000.0)
+                    }
                     // time of last data modification, human-readable
                     'y' => OutputType::Str(pretty_time(meta, MetadataTimeField::Modification)),
                     // time of last data modification, seconds since Epoch
@@ -1127,7 +1131,11 @@ impl Stater {
                     // time of last status change, human-readable
                     'z' => OutputType::Str(pretty_time(meta, MetadataTimeField::Change)),
                     // time of last status change, seconds since Epoch
-                    'Z' => OutputType::Integer(meta.ctime()),
+                    'Z' => {
+                        let (sec, nsec) = metadata_get_time(meta, MetadataTimeField::Change)
+                            .map_or((0, 0), system_time_to_sec);
+                        OutputType::Float(sec as f64 + nsec as f64 / 1_000_000_000.0)
+                    }
                     'R' => {
                         let major = meta.rdev() >> 8;
                         let minor = meta.rdev() & 0xff;

tests/by-util/test_stat.rs

@@ -194,14 +194,14 @@ fn test_char() {
 
 #[cfg(target_os = "linux")]
 #[test]
-fn test_printf_mtime_precision() {
+fn test_printf_atime_ctime_mtime_precision() {
     // TODO Higher precision numbers (`%.3Y`, `%.4Y`, etc.) are
     // formatted correctly, but we are not precise enough when we do
     // some `mtime` computations, so we get `.7640` instead of
     // `.7639`. This can be fixed by being more careful when
     // transforming the number from `Metadata::mtime_nsec()` to the form
     // used in rendering.
-    let args = ["-c", "%.0Y %.1Y %.2Y", "/dev/pts/ptmx"];
+    let args = ["-c", "%.0Y %.1Y %.2X %.2Y %.2Z", "/dev/pts/ptmx"];
     let ts = TestScenario::new(util_name!());
     let expected_stdout = unwrap_or_return!(expected_result(&ts, &args)).stdout_move_str();
     eprintln!("{expected_stdout}");