Fix Heap rmgr's desc output for infobits arrays.

Fix Heap rmgr's desc output for infobits arrays.

Make heap desc routines that output status bit as arrays of constants
avoid outputting array literals that contain superfluous punctuation
characters that complicate parsing the output.  Also make sure that no
heap desc routine repeats the same key name (at the same nesting level),
for the same reason.  Arguably, these were both oversights in commit
7d8219a4.

In passing, make the desc output code (which covers Heap's DELETE,
UPDATE, HOT_UPDATE, LOCK, and LOCK_UPDATED record types) consistent in
terms of the output order of each field.  This order also matches WAL
record struct order.  Heap's DELETE desc output now shows the record's
xmax field for the first time (just like UPDATE/HOT_UPDATE records).

Author: Peter Geoghegan <pg@bowt.ie>
Reviewed-By: Melanie Plageman <melanieplageman@gmail.com>
Discussion: https://postgr.es/m/CAH2-Wz=pNYtxiJ2Jx5Lj=fKo1OEZ4GE0p_kct+ugAUTqBwU46g@mail.gmail.com