In this PR we replace the "derived metric" introduced in #141877 with a script average or if the `aggregate_metric_double` has only one metric, with that metric.

We support the following scenarios:

- Single metric: we introduce the concept of a single metric, this is set only if the aggregate_metric_double has only one value. We saw this being used in tests when we aggregate using the min or max, but we did provide full support just in case it's used.
- Average is available: when aggregate_metric_double has the sum and value_count then we calculate the average. This is used in scripts, sorting and filtering queries.

Finally, we return no results in filtering, if none of the above apply.

Part of #128356

In this PR we replace the "derived metric" introduced in elastic#141877 with a script average or if the `aggregate_metric_double` has only one metric, with that metric.

We support the following scenarios:

- Single metric: we introduce the concept of a single metric, this is set only if the aggregate_metric_double has only one value. We saw this being used in tests when we aggregate using the min or max, but we did provide full support just in case it's used.
- Average is available: when aggregate_metric_double has the sum and value_count then we calculate the average. This is used in scripts, sorting and filtering queries.

Finally, we return no results in filtering, if none of the above apply.

Part of elastic#128356

In #141877, we deprecated
the `default_metric` of an `aggregate_metric_double`. However, the
following tests (#142544,
#142964,
#142410 &
#142477) seem to
encounter this warning even if they are not expected to set the
`default_metric`. 

In this PR, we did the following: - For #142544, we added the api group
information in the warning failure exception, so that a yaml test will
not only log the warning but it will also share more info about the api
call. - For the other two, we catch the exception in
`FieldExtractorTestCase` and log the mapping of the index, we hope that
this can help us trace if there was a template used or not. - We also
unmute the test because we cannot reproduce them locally.

In elastic#141877, we deprecated
the `default_metric` of an `aggregate_metric_double`. However, the
following tests (elastic#142544,
elastic#142964,
elastic#142410 &
elastic#142477) seem to
encounter this warning even if they are not expected to set the
`default_metric`. 

In this PR, we did the following: - For elastic#142544, we added the api group
information in the warning failure exception, so that a yaml test will
not only log the warning but it will also share more info about the api
call. - For the other two, we catch the exception in
`FieldExtractorTestCase` and log the mapping of the index, we hope that
this can help us trace if there was a template used or not. - We also
unmute the test because we cannot reproduce them locally.