Annotated text type should extend TextFieldType

[romseygeek]

The annotated text mapper has a field type that currently extends StringFieldType,
which means that all the positional-related query factory methods need to be copied
over from TextFieldType. In addition, MappedFieldType.intervals() hasn't been
overridden, so you can't use intervals queries with annotated text - a major drawback,
since one of the purposes of annotated text is to be able to run positional queries against
annotations.

This commit changes the annotated text field type to extend TextFieldType instead,
adding tests to ensure that position queries work correctly.

Closes #49289

[elasticmachine]

Pinging @elastic/es-search (:Search/Mapping)

[markharwood]

Had a quick look and I'm not sure about compatibility with intervals. How would an interval query work with this field value with a mixed-case annotation: [JFK](John+F+Kennedy)

I can't use a terms query in the interval and the match query forces lowercase because that's what the host text field uses:

{
"intervals" : {
  "headline" : {
	"all_of" : {
	  "ordered" : true,
	  "intervals" : [
		{
		  "match" : {
			"query" : "he visited",
			"max_gaps" : 0,
			"ordered" : true
		  }
		},
		{
		  "any_of" : {
			"intervals" : [
			  { "match" : { "query" : "John F Kennedy" } },
                               { "match" : { "query" : "Marilyn Monroe" } }
			]
		  }
		}
	  ]
	}
  }
}

If that's opening a can of worms maybe we can separate the "make interval queries work with annotations" into a different PR.

[jimczi]

LGTM

If that's opening a can of worms maybe we can separate the "make interval queries work with annotations" into a different PR.

+1 to address this in a follow up.

[romseygeek]

@markharwood you can specify an analyzer for an intervals match source, so if you have mixed-case or multiple-term annotations then you can query for it with analyzer: keyword

[markharwood]

LGTM - thanks, @romseygeek