pgsql: pg_clean_ascii(): escape bytes rather than lose them

pg_clean_ascii(): escape bytes rather than lose them

Rather than replace each unprintable byte with a '?' character, replace
it with a hex escape instead. The API now allocates a copy rather than
modifying the input in place.

Author: Jacob Champion <jchampion@timescale.com>
Discussion: https://www.postgresql.org/message-id/CAAWbhmgsvHrH9wLU2kYc3pOi1KSenHSLAHBbCVmmddW6-mc_=w@mail.gmail.com

Branch
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master

Details
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https://git.postgresql.org/pg/commitdiff/45b1a67a0fcb3f1588df596431871de4c93cb76f

Modified Files
--------------
src/backend/postmaster/postmaster.c |  6 +----
src/backend/utils/misc/guc.c        | 22 ++++++++++++++--
src/common/string.c                 | 52 ++++++++++++++++++++++++++++++-------
src/include/common/string.h         |  2 +-
4 files changed, 65 insertions(+), 17 deletions(-)