ES|QL: add tests for NaN on BUCKET function

[luigidellaquila]

Closes #105166

Adding tests that verify that BUCKET (previously AUTO_BUCKET) function does not return NaN when an invalid number of buckets is provided (eg. 0, -1 or a very large integer)

[elasticsearchmachine]

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

[ivancea]

Made a comment about the solution itself, and if this is really the behaviour we want.
Apart of that, looks good

[ivancea]

Should we instead validate the params in the validate() method? They are required to be foldable.
It would be a breaking change I guess, so asking to be sure

[luigidellaquila]

Thanks for checking Ivan.

[luigidellaquila]

I don't have a strong opinion on this.
It doesn't seem a critical change (it's more a corner case than a real feature) but it could be considered a breaking one.

[astefan]

LGTM

Since we are adding tests to bucket, please also add foldable expressions tests:

FROM employees | WHERE hire_date >= "1985-01-01T00:00:00Z" AND hire_date < "1986-01-01T00:00:00Z" | EVAL c = concat("2","0")::int | STATS hires_per_month = COUNT(*) BY month = BUCKET(hire_date, c, "1985-01-01T00:00:00Z", "1986-01-01T00:00:00Z") | SORT month

and

FROM employees | WHERE hire_date >= "1985-01-01T00:00:00Z" AND hire_date < "1986-01-01T00:00:00Z" | STATS hires_per_month = COUNT(*) BY month = BUCKET(hire_date, concat("2","0")::int, "1985-01-01T00:00:00Z", "1986-01-01T00:00:00Z") | SORT month