* Add ECS schema for user-agent ingest processor (#37727)
This switches the format of the user agent processor to use the schema from [ECS](https://github.com/elastic/ecs).
So rather than something like this:
```
{
"patch" : "3538",
"major" : "70",
"minor" : "0",
"os" : "Mac OS X 10.14.1",
"os_minor" : "14",
"os_major" : "10",
"name" : "Chrome",
"os_name" : "Mac OS X",
"device" : "Other"
}
```
The structure is now like this:
```
{
"name" : "Chrome",
"original" : "Mozilla/5.0 (Macintosh; Intel Mac OS X 10_14_1) AppleWebKit/537.36 (KHTML, like Gecko) Chrome/70.0.3538.102 Safari/537.36",
"os" : {
"name" : "Mac OS X",
"version" : "10.14.1",
"full" : "Mac OS X 10.14.1"
},
"device" : "Other",
"version" : "70.0.3538.102"
}
```
This is now the default for 7.0. The deprecated `ecs` setting in 6.x is not
supported.
Resolves#37329
* Remove `ecs` setting from docs