EEVEE: Remove all remaining reference of EEVEE next

This changes the engine identifier back to `BLENDER_EEVEE`.

We keep the `BLENDER_EEVEE_NEXT` identifier around for
versioning reasons (have to detect when it is the active
engine of a older file).

This also rename a bunch of pannels that were using `next`
in their name.

This is a breaking change for Addons compatibility.

Pull Request: https://projects.blender.org/blender/blender/pulls/140282

source/blender/draw/engines/overlay/overlay_instance.cc

@@ -70,7 +70,7 @@ void Instance::init()
                                          BKE_scene_uses_blender_workbench(state.scene);
     const bool viewport_uses_eevee = STREQ(
         ED_view3d_engine_type(state.scene, state.v3d->shading.type)->idname,
-        RE_engine_id_BLENDER_EEVEE_NEXT);
+        RE_engine_id_BLENDER_EEVEE);
     const bool use_resolution_scaling = BKE_render_preview_pixel_size(&state.scene->r) != 1;
     /* Only workbench ensures the depth buffer is matching overlays.
      * Force depth prepass for other render engines.