base: add nanoseconds to log timestamps.

We accidentally removed nanosecond precision at some point (likely when
I redid the formatter). This CL fixes that.

BUG=b:237004396
TEST=tested format string in the playground

Change-Id: Iaa502c13c34c9cc8f4b7be05821a63c8f10cb360
Reviewed-on: https://chromium-review.googlesource.com/c/chromiumos/platform/crosvm/+/3722782
Commit-Queue: Noah Gold <nkgold@google.com>
Reviewed-by: Daniel Verkamp <dverkamp@chromium.org>
Tested-by: kokoro <noreply+kokoro@google.com>

base/src/syslog.rs

@@ -256,7 +256,7 @@ impl State {
                 writeln!(
                     buf,
                     "[{} {:5} {}] {}",
-                    Local::now().format("%Y-%m-%dT%H:%M:%S%:z"),
+                    Local::now().format("%Y-%m-%dT%H:%M:%S%.9f%:z"),
                     record.level(),
                     record.module_path().unwrap_or("<missing module path>"),
                     record.args()