ESQL: Support advanced language features on exponential_histogram

[JonasKunz]

With #137549 we implemented the basic functionality to make exponential_histograms useful in ES|QL.
They do however still have a few language limitations, which are just there because they don't have been implemented yet.

• ENRICH support ( there currently is no EnrichResultBuilder)
• LOOKUP JOIN support ( no lookup() implementation in the block)
• multi-value support: The exponential_histogram field mapper does not support multi-values, but we could allow them to be constructed via VALUE / MV_APPEND

In the context of how exponential_histograms are used these are likely edge cases, still we should eventually support them.

[elasticsearchmachine]

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