ESQL: Support provided table for enrich

[nik9000]

Description

We've been talking on and off for a while about supporting uploading a small-ish table to the ESQL request and using it for enrich somehow. This feels like it might share building blocks with INLINE STATS - ie #106152. Maybe we can get them both at the same time?

[elasticsearchmachine]

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

[nik9000]

I'm not proposing any syntax here, just that there be some way to upload something shaped like a table as part of the request and we have some way to enrich matching rows from that table into the row stream. There's lots of ways to organize it and I'm not good to designing the language bits.