JodaCompatibleZonedDateTime in Elasticsearch 6.5.x breaks scripts with "The datetime zone id 'Z' is not recognised"

[centic9]

Elasticsearch version 6.5.1

Plugins installed: []

JVM version JVM 1.8.0_191

OS version Windows 10

Description of the problem including expected versus actual behavior:

We use scripting with date functions in some code. When we try to upgrade to Elasticsearch 6.5.1, one of our unit tests fails with the following exception:

Caused by: java.lang.IllegalArgumentException: The datetime zone id 'Z' is not recognised
	at org.joda.time.DateTimeZone.forID(DateTimeZone.java:234)
	at org.elasticsearch.script.JodaCompatibleZonedDateTime.toString(JodaCompatibleZonedDateTime.java:405)
	at java.lang.invoke.MethodHandle.invokeWithArguments(MethodHandle.java:627)
	at org.elasticsearch.painless.DefBootstrap$PIC.fallback(DefBootstrap.java:216)
	... 32 more

Steps to reproduce:

The following also reproduces this for me, it seems Joda does not know about the special "Z" timezone identifier, but Java Time uses it:

    @Test
    public void testJodaCompatibleZonedDateTime() {
        // check for an issue that we see with 6.5
        JodaCompatibleZonedDateTime dt = new JodaCompatibleZonedDateTime(Instant.EPOCH, ZoneOffset.ofTotalSeconds(0));
        assertNotNull(dt.toString("yyyy-MM-dd hh:mm", Locale.ROOT));
    }

It seems this was introduced with the Java-time-compatibility layer in commit 758a6f5 and 3046656, PR #33486

A more elaborate integration test that works at least in Elasticsearch 6.2.4, but fails with Elasticsearch 6.5.1:

  @Test
   public void testScriptDateTime() {
       index("idx", "_doc", "id1", "{ \"endTime\": 0}");
       refresh();

       final SearchRequestBuilder searchRequestBuilder = client().prepareSearch("*").
               setSize(100).
               addAggregation(AggregationBuilders.terms("script").
                       script(new Script(ScriptType.INLINE, "painless",
                               "doc['endTime'].date.toString('yyyy-MM-dd hh:mm', Locale.ROOT)", Collections.emptyMap())));
       final SearchResponse searchResponse = searchRequestBuilder.execute().actionGet();
       assertNotNull(searchResponse);
       final Terms terms = searchResponse.getAggregations().get("script");
       assertNotNull(terms.getBuckets());
       assertEquals("1970-01-01 12:00", terms.getBuckets().get(0).getKeyAsString());
       assertEquals(1, searchResponse.getHits().getTotalHits());
   }

[elasticmachine]

Pinging @elastic/es-core-infra