[ES|QL] Replace infiniteParams with minParams in fn definitions

[dej611]

Describe the feature:

There are currently 2 ways to define overlapping concepts, which is the type of variadic arguments for a function:

• infiniteParams which means "can have the current args multiple times"
• minParams which means "has to be at least N arguments, but more repeating the current signature"

For semplicity sake I think it makes more sense to use a single way to define the same concept, perhaps leveraging the more general of the two, which is the minParams. I think that infiniteParams can be rewritten with a minParams: 1 value in those few places where is defined (coalesce, greatest, least).

[elasticmachine]

Pinging @elastic/kibana-visualizations (Team:Visualizations)