SQL: Translate MIN/MAX on keyword fields as FIRST/LAST

[matriv]

Although the translation rule was implemented in the Optimizer
and the docs are in place, the rule was not added in the list of rules
to be executed.

Relates to #41195
Follows #37936

[elasticmachine]

Pinging @elastic/es-search

[astefan]

Can you add a test to QueryTranslatorTests specifically for MIN(string) and MAX(string), please?
And I would also like to see more tests in general, with these two for strings.

[matriv]

There are already tests for optimizer: https://github.com/elastic/elasticsearch/blob/master/x-pack/plugin/sql/src/test/java/org/elasticsearch/xpack/sql/optimizer/OptimizerTests.java#L1236
and
https://github.com/elastic/elasticsearch/blob/master/x-pack/plugin/sql/src/test/java/org/elasticsearch/xpack/sql/optimizer/OptimizerTests.java#L1260

Would you like to add more integration tests?

[astefan]

I missed those from OptimizerTests class; if you believe they are enough, it's ok with me. I was used to those in the QueryTranslatorTests class.

Yes, more integration tests are welcomed. The more, the better. Thanks.

[costin]

+1 on having a bit more integration tests - they don't hurt and will check potential mistakes.

[matriv]

Added also query translator tests and one more integ test.
MIN/MAX on keyword cannot be used in HAVING currently (there is a limitation documented) so I couldn't think of another integration test.

[astefan]

LGTM