Shaders changes require two or more change cycles before updating (#5142)

* Shaders changes require two or more change cycles before updating

This fixes the problem described in the title.

Consolidated the responsibility to update the root shader variant
asset into the Shader() class. It was unnecessarily spread across
Shader(), ShaderVariant() and ShaderAsset().
In particular OnAssetReloaded now makes a temporary copy of the root
ShaderVariantAsset and updates the ShaderAsset with such reference
only when OnAssetReloaded() is called on behalf of the ShaderAsset.

Signed-off-by: galibzon <66021303+galibzon@users.noreply.github.com>

Gems/AtomLyIntegration/CommonFeatures/Code/Source/DiffuseGlobalIllumination/EditorDiffuseProbeGridComponent.cpp

@@ -196,7 +196,7 @@ namespace AZ
                 {
                     // bake is complete, update configuration with the new baked texture asset
                     AzToolsFramework::ScopedUndoBatch undoBatch("DiffuseProbeGrid Texture Bake");
-                    configurationAsset = { textureAsset.GetAs<RPI::StreamingImageAsset>(), AZ::Data::AssetLoadBehavior::PreLoad };
+                    configurationAsset = textureAsset;
                     SetDirty();
 
                     if (m_controller.m_configuration.m_bakedIrradianceTextureAsset.IsReady() &&

Gems/AtomLyIntegration/CommonFeatures/Code/Source/ReflectionProbe/EditorReflectionProbeComponent.cpp

@@ -178,7 +178,7 @@ namespace AZ
                     if (notificationType == CubeMapAssetNotificationType::Ready)
                     {
                         // bake is complete, update configuration with the new baked cubemap asset
-                        m_controller.m_configuration.m_bakedCubeMapAsset = { cubeMapAsset.GetAs<RPI::StreamingImageAsset>(), AZ::Data::AssetLoadBehavior::PreLoad };
+                        m_controller.m_configuration.m_bakedCubeMapAsset = cubeMapAsset;
 
                         // refresh the currently rendered cubemap
                         m_controller.UpdateCubeMap();