Allow for docker timestamps with timezone offsets

Docker prefers to use UTC time when making images/containers,
but it's happy to parse non-UTC times too. It will then pass those on in its
output.

DateTimeFormatter.ISO_OFFSET_DATE_TIME accepts a superset of what
DateTimeFormatter.ISO_INSTANT accepts, so replace use of
ISO_INSTANT with ISO_OFFSET_DATE_TIME.

core/src/main/java/org/testcontainers/utility/DockerStatus.java

@@ -40,7 +40,7 @@ public static boolean isContainerRunning(InspectContainerResponse.ContainerState
             if (minimumRunningDuration == null) {
                 return true;
             }
-            Instant startedAt = DateTimeFormatter.ISO_INSTANT.parse(
+            Instant startedAt = DateTimeFormatter.ISO_OFFSET_DATE_TIME.parse(
                 state.getStartedAt(), Instant::from);
 
             if (startedAt.isBefore(now.minus(minimumRunningDuration))) {
@@ -75,7 +75,7 @@ public static boolean isDockerTimestampNonEmpty(String dockerTimestamp) {
         return dockerTimestamp != null
                 && !dockerTimestamp.isEmpty()
                 && !dockerTimestamp.equals(DOCKER_TIMESTAMP_ZERO)
-                && DateTimeFormatter.ISO_INSTANT.parse(dockerTimestamp, Instant::from).getEpochSecond() >= 0L;
+                && DateTimeFormatter.ISO_OFFSET_DATE_TIME.parse(dockerTimestamp, Instant::from).getEpochSecond() >= 0L;
     }
 
     public static boolean isContainerExitCodeSuccess(InspectContainerResponse.ContainerState state) {

core/src/test/java/org/testcontainers/utility/DockerStatusTest.java

@@ -66,7 +66,7 @@ public void testStopped() throws Exception {
     }
 
     private static String buildTimestamp(Instant instant) {
-        return DateTimeFormatter.ISO_INSTANT.format(instant);
+        return DateTimeFormatter.ISO_OFFSET_DATE_TIME.format(instant);
     }
 
     // ContainerState is a non-static inner class, with private member variables, in a different package.