[CF 6960] v7 - Selectivity estimation for COALESCE in eqsel/eqjoinsel

This branch was automatically generated by a robot using patches from an
email thread registered at:

https://commitfest.postgresql.org/patch/6960

The branch will be overwritten each time a new patch version is posted to
the thread, and also periodically to check for bitrot caused by changes
on the master branch.

Patch(es): https://www.postgresql.org/message-id/CAF=hKRAv48WeyDK2zC5aGacBYx0ry_QqRok2d=F53=XkUSL+jQ@mail.gmail.com
Author(s): Egor Savelev

Author: Commitfest Bot