core: merge oak-common into oak-core

oak-common is gone; its modules (configstore, xmlutils, ocioutils,
oiioutils, colormath, colortransform, videoparams, ffmpegutils, ...)
now live in oak-core alongside the value types. The render value/GPU
types moved too: backend (wgpu context + DisplayRenderer), color
(ColorProcessor over ocio-rs), texture, frame, and the commonutil
config helpers.

Fix-ups to make the merged tree build and pass tests:

- oak-core Cargo.toml: wgpu back to 25 (the moved backend code is
  written against that API generation); add the toml/quick-xml/image
  deps oak-common carried.
- lib.rs: drop the duplicate 'pub mod error;'.
- error.rs: unified OAKCORE_* codes; restore Error::new() and
  From<OcioError> from oak-common's error type.
- backend.rs/color.rs: oak_core::/oak_render:: self-references
  rewritten to crate::; the shaderfx-dependent GPU effect test moved
  to oak-render's shaderfx tests (shaderfx depends on oak-node and
  cannot live in oak-core).
- oak-render's error module re-exports oak_core::error::{Error,
  Result}; the OAKRENDER_* codes stay as the public-code contract.
- oak-node jobs.rs: ColorProcessor imported from oak_core::color.
- Integration tests repointed at oak_core::{texture, frame, backend,
  color, colormath}.
- the display-ICC regression test treats an empty OAK_DISPLAY_ICC as
  unset, matching displayicc::env_override_icc.

crates/oak-node/src/project.rs

@@ -140,29 +140,29 @@ impl Project {
 
 	/// The pipeline working colorspace (project property; ACEScg when the
 	/// setting is absent).
-	pub fn working_color_space(&self) -> oak_common::colormath::WorkingColorSpace {
-		oak_common::colormath::WorkingColorSpace::from_setting(
+	pub fn working_color_space(&self) -> oak_core::colormath::WorkingColorSpace {
+		oak_core::colormath::WorkingColorSpace::from_setting(
 			self.settings.get(SETTING_WORKING_COLOR_SPACE).map(String::as_str).unwrap_or(""),
 		)
 	}
 
 	/// The output/delivery colorspace (project property; sRGB when the
 	/// settings are absent).
-	pub fn output_color_spec(&self) -> oak_common::colormath::OutputColorSpec {
-		oak_common::colormath::OutputColorSpec::from_settings(
+	pub fn output_color_spec(&self) -> oak_core::colormath::OutputColorSpec {
+		oak_core::colormath::OutputColorSpec::from_settings(
 			self.settings.get(SETTING_OUTPUT_GAMUT).map(String::as_str).unwrap_or(""),
 			self.settings.get(SETTING_OUTPUT_TRANSFER).map(String::as_str).unwrap_or(""),
 		)
 	}
 
 	/// Set the pipeline working colorspace property.
-	pub fn set_working_color_space(&mut self, space: oak_common::colormath::WorkingColorSpace) {
+	pub fn set_working_color_space(&mut self, space: oak_core::colormath::WorkingColorSpace) {
 		self.settings
 			.insert(SETTING_WORKING_COLOR_SPACE.to_string(), space.as_setting().to_string());
 	}
 
 	/// Set the output/delivery colorspace properties.
-	pub fn set_output_color_spec(&mut self, spec: oak_common::colormath::OutputColorSpec) {
+	pub fn set_output_color_spec(&mut self, spec: oak_core::colormath::OutputColorSpec) {
 		self.settings
 			.insert(SETTING_OUTPUT_GAMUT.to_string(), spec.gamut.as_setting().to_string());
 		self.settings
@@ -357,8 +357,8 @@ impl Project {
 			_ => {}
 		}
 		// Default location: the shared disk-cache directory (single-lib:
-		// lives in oakcommon, used by oaknode and oakrender alike).
-		oak_common::filefunctions::default_disk_cache_path()
+		// lives in oak_core, used by oaknode and oakrender alike).
+		oak_core::filefunctions::default_disk_cache_path()
 	}
 
 	/// Copy all settings from `src` into `self` (C++