fix: explicitly default TableScanBuilder move ctor for Windows DLL export

MSVC does not export the implicitly-generated move constructor of a
template class instantiation. RestTableScanBuilder (introduced in
iceberg_rest) is exported with ICEBERG_REST_EXPORT, so its compiler-
generated move constructor must call the base TableScanBuilder move
constructor as an imported symbol. Explicitly defaulting it makes it
part of the explicit template instantiation and therefore exported.

Author: Sandeep Gottimukkala

src/iceberg/table_scan.h

@@ -397,6 +397,9 @@ class ICEBERG_TEMPLATE_CLASS_EXPORT TableScanBuilder : public ErrorCollector {
                    std::string table_name,
                    std::shared_ptr<MetricsReporter> metrics_reporter);
 
+  TableScanBuilder(TableScanBuilder&&) = default;
+  TableScanBuilder& operator=(TableScanBuilder&&) = default;
+
   // Return the schema bound to the specified snapshot.
   Result<std::reference_wrapper<const std::shared_ptr<Schema>>> ResolveSnapshotSchema();
   Status ResolveColumnStatsSelection();