This makes a `parentCardinality` available to every `Aggregator`'s ctor
so it can make intelligent choices about how it collects bucket values.
This replaces `collectsFromSingleBucket` and is similar to it but:
1. It supports `NONE`, `ONE`, and `MANY` values and is generally
extensible if we decide we can use more precise counts.
2. It is more accurate. `collectsFromSingleBucket` assumed that all
sub-aggregations live under multi-bucket aggregations. This is
normally true but `parentCardinality` is properly carried forward
for single bucket aggregations like `filter` and for multi-bucket
aggregations configured in single-bucket for like `range` with a
single range.
While I was touching every aggregation I renamed `doCreateInternal` to
`createMapped` because that seemed like a much better name and it was
right there, next to the change I was already making.
Relates to #56487
Co-authored-by: Elastic Machine <elasticmachine@users.noreply.github.com>
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