Add WRITE_*_ARRAY macros

Add WRITE_ATTRNUMBER_ARRAY, WRITE_OID_ARRAY, WRITE_INT_ARRAY,
WRITE_BOOL_ARRAY macros to outfuncs.c, mirroring the existing
READ_*_ARRAY macros in readfuncs.c.
Reviewed-by: Tom Lane <tgl@sss.pgh.pa.us>
Discussion: https://www.postgresql.org/message-id/flat/8f2ebc67-e75f-9478-f5a5-bbbf090b1f8d%402ndquadrant.com