Core: Add java time xcontent serializers

[spinscale]

This ensures that the java time class exposed by painless have proper
serialization/string representations.

Closes #31853

[elasticmachine]

Pinging @elastic/es-core-infra

[nik9000]

I don't know enough to review any of the changes to the DateFormatters file but the other changes look good to me.

[rjernst]

LGTM

[spinscale]

the formatter changes fix one small issue in printing out the wrong format, but add a new format which contains more granularity than 999 milliseconds, as this is already done this way in our current ingest code and this remains BWC compatible to the current way of doing things.

One minor change introduced with this one is now, that dates that have a value of 0 milliseconds, those milliseconds are now always printed out - before that one could end up with those milliseconds being removed. I think this is fine for us though.

[courtneycouch]

@spinscale Looks like this extends beyond Java time on more recent ES versions:

cannot write xcontent for unknown value of type class org.apache.lucene.search.SortField$2

For example when getting _segments on indexes with lucene sort configurations.

[spinscale]

@courtneycouch can you share your index mapping and index sorting configuration and also provide the version you tested again, and if you got a full stack trace? Also feel free to open a new issue if you want as this is surely not fixed with this PR.

[courtneycouch]

The simplest way to reproduce it is to do the following on 6.4.0

PUT test_index
{
  "settings": {
    "index": {
      "sort": {"field": ["field_1"]}
    }
  },
  "mappings": {
    "doc": {
      "properties": {
        "field_1": {"type": "keyword"}
      }
    }
  }
}

POST test_index/doc/1
{
 "field_1": "foo"
}

GET test_index/_segments

[courtneycouch]

Just to add, it works when using a numeric field type. I haven't tested other non-numeric types, I just know when using a keyword type it breaks.

[spinscale]

thanks for the reproduction! I used a date field and it did not reproduce... I'll take a look an open an issue.

[spinscale]

FYI: I opened #33414