pgsql: Fix incorrect xmlschema output for types timetz and timestamptz.

Fix incorrect xmlschema output for types timetz and timestamptz.

The output of table_to_xmlschema() and allied functions includes
a regex describing valid values for these types ... but the regex
was itself invalid, as it failed to escape a literal "+" sign.

Report and fix by Renan Soares Lopes.  Back-patch to all
supported branches.

Discussion: https://postgr.es/m/7f6fabaa-3f8f-49ab-89ca-59fbfe633105@me.com

Branch
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REL_14_STABLE

Details
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https://git.postgresql.org/pg/commitdiff/ae8ec7febac1b414681c16022e6c655a62a2540a

Modified Files
--------------
src/backend/utils/adt/xml.c            |   4 +-
src/test/regress/expected/xmlmap.out   | 928 ++++++++++++++++++---------------
src/test/regress/expected/xmlmap_1.out |  10 +-
src/test/regress/sql/xmlmap.sql        |  10 +-
4 files changed, 514 insertions(+), 438 deletions(-)