Add millisecond parser for dynamic date fields mapped from "yyyy/MM/dd"

[jasontedor]

Dynamic date fields mapped from dates of the form "yyyy-MM-dd"
automatically receive the millisecond paresr epoch_millis as an
alternative parsing format. However, dynamic date fields mapped from
dates of the form "yyyy/MM/dd" do not. This is a bug since the migration
documentation currently specifies that a dynamically added date field,
by default, includes the epoch_millis format. This commit adds
epoch_millis as an alternative parser to dynamic date fields mapped from
dates of the form "yyyy/MM/dd".

Closes #12873

[rjernst]

LGTM

[RicherdLee]

I use 1.7.2
I set mapping like this
"mappings": {
"enlink_query_record": {
"properties": {
"ordertime": {
"type": "date",
"format": "yyyy/MM/dd HH:mm:ss"
}
}
}
}

when i syn data,the ordertime still display

I'm not sure whether it's millisecond parser for dynamic date fields problem。
shoud id change 2.0.0
Thinks