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_16_STABLE

Details
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https://git.postgresql.org/pg/commitdiff/77763f3bef482f575fd51190f27f38d3bc5ba42a

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(-)