QPropertyBindingSourceLocation: make (source_location) ctor constexpr

The typical argument, source_location::current(), is consteval, so it
cannot actually be used outside constexpr contexts. Having a
non-consteval, non-constexpr ctor to accept the return value is
conceptually wrong, as a constexpr-only result is forced though a
non-constexpr function. It may even trigger MSVC's consteval bug:

  https://developercommunity.visualstudio.com/t/Cannot-use-std::source_location-in-C-m/1436152

because the work-around given, wrapping in a lambda, means wrapping
the result in a constexpr context, and that may just be the root cause
of the issue.

Pick-to: 6.3 6.2
Change-Id: I49534cf86f32e16b13d7e169cd5cb0c8fc374d69
Reviewed-by: Fabian Kosmale <fabian.kosmale@qt.io>

src/corelib/kernel/qproperty.h

@@ -112,7 +112,7 @@ struct Q_CORE_EXPORT QPropertyBindingSourceLocation
     quint32 column = 0;
     QPropertyBindingSourceLocation() = default;
 #ifdef QT_PROPERTY_COLLECT_BINDING_LOCATION
-    QPropertyBindingSourceLocation(const QT_SOURCE_LOCATION_NAMESPACE::source_location &cppLocation)
+    constexpr QPropertyBindingSourceLocation(const QT_SOURCE_LOCATION_NAMESPACE::source_location &cppLocation)
     {
         fileName = cppLocation.file_name();
         functionName = cppLocation.function_name();