Add support for runtime fields to mappings editor

[cjcenizal]

Runtime fields have been added to Elasticsearch via elastic/elasticsearch#61776. We need to add support for editing this field in the mappings editor, similar to the screenshot below.

API

Here's an example of defining runtime fields via the API:

PUT /my-index/_mappings
{
    "properties" : {
        "day_of_week" : {
            "type" : "runtime",
            "runtime_type" : "keyword",
            "script" : {
                "source" : "emitValue(doc['timestamp'].value.dayOfWeekEnum.getDisplayName(TextStyle.FULL, Locale.ROOT))"
            }
        }
    }
}

The supported runtime_type values are:

• keyword
• long
• double
• date
• ip
• boolean

[elasticmachine]

Pinging @elastic/es-ui (Team:Elasticsearch UI)