ESQL: AUTO_BUCKET() can return NaN

[bpintea]

Description

Specifying a zero as the number of buckets with numeric field will return NaN instead of null (due to div by 0).
Ex: ROW AUTO_BUCKET(1, 0, 0, 0)

Same for negative number of buckets (due to log10(negative)).
Ex: ROW AUTO_BUCKET(1, -1, 0, 0)

Same for a number of buckets value that wraps over int (due to int overflow).
Ex: ROW AUTO_BUCKET(0, 100000000000, 0, 0)

Related: #98698.

[elasticsearchmachine]

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

[luigidellaquila]

This issue does not seem to reproduce anymore.
AUTO_BUCKET function was renamed as BUCKET and is now only allowed as a grouping function, so the queries above return a validation exception.

The following queries return NULL as expected.

ROW a = 1 | stats max(a) by BUCKET(1, 0, 0, 0)
ROW a = 1 | stats max(a) by BUCKET(1, -1, 0, 0)
ROW a = 1 | stats max(a) by BUCKET(0, 100000000000, 0, 0)

Internally, some parts of the code still produce a NaN, but downstream it is resolved to NULL.

I'll add some tests, then I think this can be closed.