ES|QL Empty index resolution

[idegtiarenko]

Before this change FROM data,index-* is successfully resolves to data index only but FROM index-* fails.
This change aligns behavior by always allowing empty index resolutions in * patterns.
Now index resolution is also consistent with GET /data,index-*/_search and GET /index-*/_search.

Related to: S2D24

[elasticsearchmachine]

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

[elasticsearchmachine]

Hi @idegtiarenko, I've created a changelog YAML for you. Note that since this PR is labelled >breaking, you need to update the changelog YAML to fill out the extended information sections.

[luigidellaquila]

IMHO it makes sense.

The only thing that doesn't really make much sense to me is the result:

from nothing*

{
    "columns": [
        {
            "name": "<no-fields>",
            "type": "null"
        }
    ],
    "values": []
}

That <no-fields> could be problematic, also because it sticks there even if you add new fields with EVAL.

Since we are moving towards accepting empty plans, it would make sense to return no columns.

[idegtiarenko]

Replaced with #135826