pgsql: Add attstattarget to FormExtraData_pg_attribute

Add attstattarget to FormExtraData_pg_attribute

This allows setting attstattarget when a relation is created.

We make use of this by having index_concurrently_create_copy() copy
over the attstattarget values when the new index is created, instead
of having index_concurrently_swap() fix it up later.

Reviewed-by: Tomas Vondra <tomas(dot)vondra(at)enterprisedb(dot)com>
Discussion: https://www.postgresql.org/message-id/flat/4da8d211-d54d-44b9-9847-f2a9f1184c76(at)eisentraut(dot)org

Branch
------
master

Details
-------
https://git.postgresql.org/pg/commitdiff/6a004f1be87d34cfe51acf2fe2552d2b08a79273

Modified Files
--------------
src/backend/catalog/heap.c | 5 +-
src/backend/catalog/index.c | 97 +++++++++++---------------------------
src/backend/catalog/toasting.c | 2 +-
src/backend/commands/indexcmds.c | 2 +-
src/include/catalog/index.h | 1 +
src/include/catalog/pg_attribute.h | 1 +
6 files changed, 36 insertions(+), 72 deletions(-)