Fix worker-thread and linkage crashes

Scalar and cast bodies run MEOS on DuckDB TaskScheduler worker threads, which
need a per-thread meos_initialize(); a thread-local guard in the scalar exec
wrapper and a cast trampoline (RegisterMeosCastFunction) cover every entry
point, so timestamp formatting no longer dereferences a NULL session_timezone.
Per-type DuckDB callbacks and blob helpers have internal linkage and a single
canonical blob round-trip (TemporalToBlob / BlobToTemporal) declared once in
temporal/temporal_blob.hpp, so each function-pointer registration binds to its
own body.

(cherry picked from commit 7b99a0c)

Author: estebanzimanyi

CMakeLists.txt

@@ -59,6 +59,7 @@ set(EXTENSION_SOURCES
     src/spatial_ref_sys_csv.inc
     src/mobilityduck_extension.cpp        
     src/temporal/temporal.cpp
+    src/temporal/temporal_blob.cpp
     src/temporal/temporal_functions.cpp
     src/temporal/temporal_aggregates.cpp
     src/temporal/tbox.cpp