pgsql: Tidy-up some appendStringInfo*() usages

Tidy-up some appendStringInfo*() usages

Make a few newish calls to appendStringInfo() which have no special
formatting use appendStringInfoString() instead. Also, adjust usages of
appendStringInfoString() which only append a string containing a single
character to make use of appendStringInfoChar() instead.

This makes the code marginally faster, but primarily this change is so
we use the StringInfo type as it was intended to be used.

Discussion: https://postgr.es/m/CAApHDvpXKQmL+r=VDNS98upqhr9yGBhv2Jw3GBFFk_wKHcB39A@mail.gmail.com

Branch
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master

Details
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https://git.postgresql.org/pg/commitdiff/2075ba9dc9af8833b1147996c15246e44a1e4fab

Modified Files
--------------
src/backend/access/rmgrdesc/heapdesc.c | 6 +++---
src/backend/access/rmgrdesc/nbtdesc.c | 2 +-
src/backend/access/rmgrdesc/rmgrdesc_utils.c | 2 +-
src/backend/access/transam/xlogbackup.c | 2 +-
src/backend/replication/slot.c | 2 +-
src/backend/utils/adt/ruleutils.c | 4 ++--
src/test/regress/pg_regress.c | 4 ++--
7 files changed, 11 insertions(+), 11 deletions(-)