Add EU7 PACK v11 UTEX, section unload, and LRU streaming caches

Bake deduplicated section texture lists (UTEX) and read them at runtime so
texture warm/prefetch no longer scans every instance. Evict PACK sections
outside a 16 km keep ring and cap mesh/nodedata/texture warm caches to stop
RAM and apply cost from growing without bound during long fast camera flight.

- Bake v11 (format=4): UMES + UTEX + CHNK; mesh/texture ordering by frequency
- Runtime: incremental UTEX warm, adaptive apply slices, preempt/catchup tuning
- Unload: track instances per section, Region erase, pack pool release
- LRU: mesh/nodedata (2000, ref-counted), warmed textures (2048)
- Bench/diagnostics: unload and cache eviction counters
- Fix pack instance erase in Region; resolve duplicate helper symbols

rendering/particles.h

@@ -181,6 +181,8 @@ public:
         insert( std::string const &Sourcetemplate, TDynamicObject const *Vehicle, glm::dvec3 const Location );
     bool
         insert( std::string const &Sourcetemplate, TAnimModel const *Node, glm::dvec3 const Location );
+    void
+        erase_bound_node( TAnimModel const *Node );
     // updates state of all owned emitters
     void
         update();