* Add aggregation support for derived fields

Signed-off-by: Marc Handalian <marc.handalian@gmail.com>

* add unit test for a terms agg with derived fields

Signed-off-by: Marc Handalian <marc.handalian@gmail.com>

* Fix license header and add changelog entry

Signed-off-by: Marc Handalian <marc.handalian@gmail.com>

* move matrix_stats tests to aggs-matrix-stats module

Signed-off-by: Marc Handalian <marc.handalian@gmail.com>

* Move matrix tests back and add dependency to painless module

Signed-off-by: Marc Handalian <marc.handalian@gmail.com>

* add tests for all aggregations types and support ip_range

Signed-off-by: Marc Handalian <marc.handalian@gmail.com>

* Add tests for agg script returned from DerivedFieldType

Signed-off-by: Marc Handalian <marc.handalian@gmail.com>

* remove children aggs test as its not yet supported

Signed-off-by: Marc Handalian <marc.handalian@gmail.com>

* Add more tests

Signed-off-by: Marc Handalian <marc.handalian@gmail.com>

* fix changelog

Signed-off-by: Marc Handalian <marc.handalian@gmail.com>

---------

Signed-off-by: Marc Handalian <marc.handalian@gmail.com>
(cherry picked from commit e26608b)
Signed-off-by: github-actions[bot] <github-actions[bot]@users.noreply.github.com>

These tests fail to backport to 2.x becuase 2.x uses a different branch of
tdigest that computes percentiles differently.  Rather than chase these over time,
change the assertions to check for the length of results returned instead of their values.

Signed-off-by: Marc Handalian <marc.handalian@gmail.com>
(cherry picked from commit 0cde7ba)
Signed-off-by: Marc Handalian <marc.handalian@gmail.com>