Remove duplicate CIDR funcs by using coerce entries.

src/backend/parser/parse_coerce.c

src/backend/utils/adt/inet.c

src/include/catalog/pg_amop.h

src/include/catalog/pg_operator.h

src/include/catalog/pg_proc.h

src/include/catalog/pg_type.h

src/include/parser/parse_coerce.h

src/include/utils/builtins.h