Rename ii_KeyAttrNumbers to ii_IndexAttrNumbers to prevent confusion with
ii_NumIndexAttrs/ii_NumIndexKeyAttrs. ii_IndexAttrNumbers contains
all attributes including "including" columns, not only key attribute.

Discussion: https://www.postgresql.org/message-id/13123421-1d52-d0e4-c95c-6d69011e0595%40sigaev.ru