pgsql: Fix XMLTABLE() deparsing to quote namespace names if necessary.

Fix XMLTABLE() deparsing to quote namespace names if necessary.

When deparsing an XMLTABLE() expression, XML namespace names were not
quoted. However, since they are parsed as ColLabel tokens, some names
require double quotes to ensure that they are properly interpreted.
Fix by using quote_identifier() in the deparsing code.

Back-patch to all supported versions.

Dean Rasheed, reviewed by Tom Lane.

Discussion: https://postgr.es/m/CAEZATCXTpAS%3DncfLNTZ7YS6O5puHeLg_SUYAit%2Bcs7wsrd9Msg%40mail.gmail.com

Branch
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REL_15_STABLE

Details
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https://git.postgresql.org/pg/commitdiff/7c0379516f367cf6a3709c46b2fed12777468130

Modified Files
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src/backend/utils/adt/ruleutils.c | 3 ++-
src/test/regress/expected/xml.out | 10 +++++++---
src/test/regress/expected/xml_1.out | 8 +++++---
src/test/regress/expected/xml_2.out | 10 +++++++---
src/test/regress/sql/xml.sql | 8 +++++---
5 files changed, 26 insertions(+), 13 deletions(-)