ESQL: reuse agg filter evaluation across multiple aggs in compute #116720
Description
Description
For a query like...
STATS c = count(*) WHERE a > 1,
m = max(field) WHERE a > 1
BY some_field
(Note: the BY will prevent the filter to be extracted outside the STATS, once #115678 is merged.)
...we're evaluating the same WHERE a > 1 twice - instead of evaluating it per agg, we should reuse its evaluation. This impacts the actual aggregation execution, to reuse the mask/input block across aggregations.
Ideally, we'd also be able to fuse masks, in case the second agg would look smth like m = max(field) WHERE a > 1 AND other_field > 0.
Related #114352