GPU: Make nodetree GLSL Codegen render engine agnostic

This commit removes all EEVEE specific code from the `gpu_shader_material*.glsl`
files. It defines a clear interface to evaluate the closure nodes leaving
more flexibility to the render engine.

Some of the long standing workaround are fixed:
- bump mapping support is no longer duplicating a lot of node and is instead
  compiled into a function call.
- bump rewiring to Normal socket is no longer needed as we now use a global
  `g_data.N` for that.


Closure sampling with upstread weight eval is now supported if the engine needs
it.

This also makes all the material GLSL sources use `GPUSource` for better
debugging experience. The `GPUFunction` parsing now happens in `GPUSource`
creation.

The whole `GPUCodegen` now uses the `ShaderCreateInfo` and is object type
agnostic. Is has also been rewritten in C++.

This patch changes a view behavior for EEVEE:
- Mix shader node factor imput is now clamped.
- Tangent Vector displacement behavior is now matching cycles.
- The chosen BSDF used for SSR might change.
- Hair shading may have very small changes on very large hairs when using hair
  polygon stripes.
- ShaderToRGB node will remove any SSR and SSS form a shader.
- SSS radius input now is no longer a scaling factor but defines an average
  radius. The SSS kernel "shape" (radii) are still defined by the socket default
  values.

Appart from the listed changes no other regressions are expected.

1 files changed, 2 insertions, 13 deletions

diff --git a/source/blender/makesdna/DNA_node_types.h b/source/blender/makesdna/DNA_node_types.h
index 5f909ea325b..1b9192c75cf 100644
--- a/source/blender/makesdna/DNA_node_types.h
+++ b/source/blender/makesdna/DNA_node_types.h
@@ -318,23 +318,12 @@ typedef struct bNode {
   short preview_xsize, preview_ysize;
   /** Used at runtime when going through the tree. Initialize before use. */
   short tmp_flag;
-  /** Used at runtime to tag derivatives branches. EEVEE only. */
-  char branch_tag;
+
+  char _pad0;
   /** Used at runtime when iterating over node branches. */
   char iter_flag;
 
   /**
-   * XXX: eevee only, id of screen space reflection layer,
-   * needs to be a float to feed GPU_uniform.
-   */
-  float ssr_id;
-  /**
-   * XXX: eevee only, id of screen subsurface scatter layer,
-   * needs to be a float to feed GPU_uniform.
-   */
-  float sss_id;
-
-  /**
    * Describes the desired interface of the node. This is run-time data only.
    * The actual interface of the node may deviate from the declaration temporarily.
    * It's possible to sync the actual state of the node to the desired state. Currently, this is