ES|QL: Add unsigned long and mixed numeric types support to Decay function

[timgrein]

Follow-up for #132729.

This PR adds unsigned_long support to the decay(...) function

[elasticsearchmachine]

Pinging @elastic/es-search-relevance (Team:Search Relevance)

[github-actions]

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[carlosdelest]

It's a good start! But I think it doesn't address unsigned long values - please check the comments

[carlosdelest]

Check how unsigned long test cases are generated for some ideas on how to generate numbers that don't fit into long

[carlosdelest]

I wonder if it's enough to check if origin and scale are numeric? It should be possible to mix and match numeric types, i.e. use an unsigned long origin but an int scale etc

[timgrein]

That's a good point, I wanted to restrict it first to make it a bit simpler, but giving it a second thought it definitely makes sense to support mixed numeric types.

Adjusted with:

• Support mixed numeric types for numeric decay
• Add mixed numeric types test cases

Full disclosure: we need to the same for offset. I'll add it to #134789, which I've opened yesterday and address it in a separate PR.

[carlosdelest]

I think you can use EsqlDataTypeConverter.convert() here

[timgrein]

Right! Adjusted with Use EsqlDataTypeConverter for most cases.

[carlosdelest]

LGTM, thanks @timgrein !