Add randomized testing for TS command

[kkrik-es]

Use randomized data-sets and aggregation queries to test our ESQL implementation for querying time-series, for producing correct results.

[elasticsearchmachine]

Pinging @elastic/es-analytical-engine (Team:Analytics)

[elasticsearchmachine]

Pinging @elastic/es-storage-engine (Team:StorageEngine)

[pabloem]

once we merge #134330 we should be good to close this!

[luigidellaquila]

Just passing by, may I suggest to also add a generator for TS command in the Generative tests?
See https://github.com/elastic/elasticsearch/blob/main/x-pack/plugin/esql/qa/server/src/main/java/org/elasticsearch/xpack/esql/qa/rest/generative/command/source/FromGenerator.java

[kkrik-es]

This is on our radar, Luigi. We started with a separate test to iterate fast for 9.2, and we're separately looking at TS Generative tests in #133804. This is promising, though, it'd be nice to extend Generative tests to check output as in our (more controlled) randomized tests.

[luigidellaquila]

Thanks for the pointer @kkrik-es !
Output checks are not always possible unfortunately because the results are non-deterministic (eg. when there is no SORT in the query). We have ideas to solve the problem, so probably in future we'll be able to do it.