Make keyword a family of field types

[markharwood]

This change introduces a familyTypeName method to MappedFieldType for use in the field capabilities API.
The constant_keyword and wildcard fields override this to return keyword to describe the family to which they belong.

Relates to #53175

[elasticmachine]

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

[markharwood]

@costin - do you have any pointers for the best place to reset the SQL expectations that are failing here (see test output) now that I've changed the field capabilities as per what we agreed in #53175 ?

[jimczi]

do you have any pointers for the best place to reset the SQL expectations that are failing here (see test output) now that I've changed the field capabilities as per what we agreed in #53175 ?

I guess we have no choice but to replace all instance of constant_keyword by keyword in SQL. It seems that most of the errors are on the test expectation that should be changed to keyword or KEYWORD depending on the context ?

[markharwood]

I got a little lost chasing expected vs actuals discrepancies when it looks like a lot of the expectations might come from *csv-spec files.

[costin]

@markharwood you're on the right path. The *.csv-spec files are the ones that indicate what we expect. For example:
org.elasticsearch.xpack.sql.qa.security.JdbcCsvSpecIT.test {alias.testDescribeAlias} indicates there's a failure inside alias.csv-spec for describeAlias, namely here.

Hope this helps.

[costin]

Tagging @astefan for awareness since once this PR lands, we should remove the constant_keyword handling.

[astefan]

LGTM

[jimczi]

LGTM, we should also update the documentation in _field_caps to explain the keyword family ?

[jtibshirani]

@markharwood perhaps we should make a note in the migration/ breaking changes docs for 7.x explaining that constant_keyword is now presented as keyword.