Jernej Klancic d615add1b1 Add pipeline parent validation for auto date histogram (#35670)
Allow `auto_date_histogram` as a valid parent agg for derivative, 
cumulative sum, moving average, moving function and serial 
differencing pipeline aggregations.

Since all these aggs share the same requirement (sequentially
ordered parent aggs), this commit also refactors to share
the same validation code so that any newly added aggs won't
be forgotten.

Closes #35578
2018-12-10 16:02:49 -05:00
..