pgsql: Properly schema-qualify additional object types ingetObjectDesc

Properly schema-qualify additional object types in getObjectDescription().

Collations, conversions, extended statistics objects (in >= v10),
and all four types of text search objects have schema-qualified names.
getObjectDescription() ignored that and would emit just the base name of
the object, potentially producing wrong or at least highly misleading
output.  Fix it to add the schema name whenever the object is not "visible"
in the current search path, as is the rule for other schema-qualifiable
object types.

Although in common situations the output won't change, this seems to me
(tgl) to be a bug worthy of back-patching, hence do so.

Kyotaro Horiguchi, per a complaint from me

Discussion: https://postgr.es/m/20180522.182020.114074746.horiguchi.kyotaro@lab.ntt.co.jp

Branch
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REL9_6_STABLE

Details
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https://git.postgresql.org/pg/commitdiff/3d3165210dccff489e3082b96f4b5c0d4ade37ff

Modified Files
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src/backend/catalog/objectaddress.c         | 76 ++++++++++++++++++++++++++---
src/test/regress/expected/alter_generic.out | 10 ++--
src/test/regress/expected/alter_table.out   | 10 ++--
3 files changed, 80 insertions(+), 16 deletions(-)