Randomized testing against match_only_text

[jdcryans]

• Improve text/keyword field multi-field testing. Test each field type as child field of all other field types.
• Pattern_text and match_only_text comparison testing

[elasticsearchmachine]

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

[kkrik-es]

We have some coverage for multi-fields:
https://github.com/elastic/elasticsearch/blob/main/test/framework/src/main/java/org/elasticsearch/datageneration/datasource/DefaultMappingParametersHandler.java#L207

We need to generalize this:

• Check more combinations: keyword - text, match_only_text - keyword, keyword - match_only_text
• Apply ignore_above and other parameters that may affect synthetic source to parent and children fields this is done already, maybe increase frequency

We also need to add testing in querying for multi-fields when configured - this is where we see these errors. For instance, this file contains the list of queries used for testing:
https://github.com/elastic/elasticsearch/blob/main/x-pack/plugin/logsdb/src/javaRestTest/java/org/elasticsearch/xpack/logsdb/qa/StandardVersusLogsIndexModeChallengeRestIT.java

[parkertimmins]

@kkrik-es

Does in make sense to include wildcard multi-fields? Presumably both as the main field and the sub-field.
So we'll be testing text, keyword, match_only_text, wildcard, patterned_text.
Does it makes sense to test all combinations of main and sub-field? Sure, having main match_only_text field with a text sub-field is a very weird things to do ... but it should still work, right?

[kkrik-es]

Right, let's add all options if possible and let randomization do its thing.. Maybe there's a separate test where we force multi-field configurations more aggressively.