pgsql: Resolve unknown-type literals in property expressions

Resolve unknown-type literals in property expressions

When a string literal is provided as a property expression, the data
type of the property was set to "unknown", which may lead to various
failures when the property is used in GRAPH_TABLE or when its data
type is compared against other properties with the same name. To fix
this, call resolveTargetListUnknowns() on the targetlist of new
properties being added to resolve unknown type literals.

Reported-by: Noah Misch <noah(at)leadboat(dot)com>
Author: Ashutosh Bapat <ashutosh(dot)bapat(dot)oss(at)gmail(dot)com>
Discussion: https://www.postgresql.org/message-id/flat/20260630173053.51.noahmisch%40microsoft.com

Branch
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REL_19_STABLE

Details
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https://git.postgresql.org/pg/commitdiff/b820c623dd5090ef69b8b8151a0b152f5d976fed

Modified Files
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src/backend/commands/propgraphcmds.c | 2 ++
.../regress/expected/create_property_graph.out | 37 +++++++++++++++++-----
src/test/regress/sql/create_property_graph.sql | 5 +++
3 files changed, 36 insertions(+), 8 deletions(-)