refactor(node,render): route oaknode->oakrender calls through the C ABI

- oakrender cache C API: add create_for_node (four cache kinds),
  get_uuid, request, load/save_state, set_saving_enabled,
  set_passthrough, get_passthroughs, get_valid_cache_filename,
  get_timebase, lock/unlock, invalidate_range (rational variant),
  get_native (C++ only, for the in-module PreviewAutoCacher)
- Node's four caches become owned OakRenderCache value handles; all
  cache access in node.cpp/clip/viewer/traverser/serializers goes
  through the C ABI
- oaknode_node_get_video_frame_cache returns an addref'd
  OakRenderCache; drop OakNodeFrameCache; oaktask precache/export and
  oakrender_video_ticket_params take the value handle
- color: OCIOBaseNode/OCIOLutNode hold OakColorProcessor handles
  (dtors added); oakrender gains color_processor_create_transform/
  create_lut/create_grading_primary/get_native and LUT library
  queries, keeping all OCIO transform construction inside oakrender;
  oaknode gains colormanager_wrap_borrowed/get_native
- RenderManager::instance() check -> oakrender_manager_available();
  cancel_video_tasks and disk cache path go through manager C API
- remaining node->render C++ symbol: only olive::Texture::~Texture
  via Variant's shared_ptr payload (recorded exception, same class as
  the UndoCommand inheritance)

Tests: new cache/color/manager/colormanager cases; all standalone
trees green (common 196, codec 22, audio 40, task 112, render 63,
timeline 125, node 98, plugin 102).

include/node/node.h

@@ -134,7 +134,7 @@ struct OakTimelineWorkArea;
  * (olive::FrameHashCache in oakrender). oakrender reinterprets this into
  * its own handle types.
  */
-typedef struct OakNodeFrameCache OakNodeFrameCache;
+struct OakRenderCache;
 
 /* oakcore handles used by the viewer setters. */
 typedef struct OakAudioParams OakAudioParams;
@@ -575,11 +575,14 @@ int oaknode_node_get_work_area(OakNodeNode node,
 							   struct OakTimelineWorkArea *out);
 
 /**
- * @brief Borrowed video frame cache of a node (NULL when the node has
- *        none or for an empty handle).
+ * @brief Video frame cache of a node as an addref'd oakrender value
+ *        handle (release with oakrender_cache_free()). *out is an
+ *        empty handle (ctx == NULL) when the node has none or for an
+ *        empty node handle. struct OakRenderCache is forward-declared
+ *        here; include render/cache.h for the definition.
  */
 int oaknode_node_get_video_frame_cache(OakNodeNode node,
-									   OakNodeFrameCache **out);
+									   struct OakRenderCache *out);
 
 /**
  * @brief Copy input values/connections from one node to another