refactor(codec): de-Qt oakcodec and wrap it in a pure C ABI; switch common handles to refcounted value structs

- oakcodec: de-Qt all 20 sources (QThread decode loop -> std::thread,
  QObject/signals -> callbacks), pure C ABI in include/codec with
  refcounted neutral handles (OakFrame/OakDecoder/OakEncoder),
  framemanager moved in from render, frame_to_buffer/buffer_to_frame
  moved in from oakcommon oiioutils, codec->task via submit callback
  (M8 will register), all cross-module calls go through the other
  side's C API, -fvisibility=hidden + OAKCODEC_API
- oakcommon: handles become refcounted value structs
  {ctx, addref, release, abi_version} (FFmpeg-style), pass-by-value
  signatures, free() as release wrapper; init_from_native/get_native
  for copyable value objects; OakCommonXxx renamed to OakXxx
- oakcommon: add logging (log_debug/info/warning/critical with level
  filtering and sink injection) + printf-style oakcommon_log C wrapper
- oakrender: add CancelAtom C API family; complete
  oakrender_color_processor_convert_frame; fix get_processor() missing
  definition and OCIO env var lookup
- tests: oakcommon 174, oaknode 96, oakrender 42, oakcodec 18, all
  green in their standalone builds

include/node/colormanager.h

@@ -174,13 +174,13 @@ int oaknode_colormanager_get_default_luma_coefs(OakNodeColorManager *manager,
  * colorspace) is clamped to what the active config offers
  * (olive::ColorManager::get_compliant_color_space(ColorTransform, bool)).
  *
- * `out` receives a NEW handle owned by the caller (release with
- * oakcommon_colortransform_free()). Requires a loaded config
- * (OAKNODE_E_STATE otherwise).
+ * `out` receives a NEW by-value handle owned by the caller (reference
+ * count 1, release with oakcommon_colortransform_free()). Requires a
+ * loaded config (OAKNODE_E_STATE otherwise).
  */
 int oaknode_colormanager_get_compliant_color_transform(
-	OakNodeColorManager *manager, const OakCommonColorTransform *transform,
-	int force_display, OakCommonColorTransform **out);
+	OakNodeColorManager *manager, OakColorTransform transform,
+	int force_display, OakColorTransform *out);
 
 #ifdef __cplusplus
 }