Add a type NumericTime to make sorting possible without performance tradeoffs

[varfrog]

OpenSearch 2.17 indexes "date" fields (even with format=epoch_seconds) as text:

                            "type": "text",
                            "fields": {
                                "keyword": {
                                    "type": "keyword",
                                    "ignore_above": 256
                                }
                            }

Sorting on such a field gives:

Text fields are not optimised for operations that require per-document field data like aggregations and sorting, so these operations are disabled by default. Please use a keyword field instead. Alternatively, set fielddata=true on [<field name>] in order to load field data by uninverting the inverted index. Note that this can use significant memory.