FbxImportRequestHandler is now loaded only once per AssetBuilder and Editor + re-enabled STL support (#933)

* Revert "FBX settings can be opened again: g_fbxImporter is set, and if the ex… (#878)"

This reverts commit 58adcf168f.

* Revert "Merge pull request #753 from aws-lumberyard-dev/Helios_DataDrivenAssetImporter"

This reverts commit 798d96f1a2, reversing
changes made to eb31d90ad9.

* Revert "Revert "Merge pull request #753 from aws-lumberyard-dev/Helios_DataDrivenAssetImporter""

This reverts commit c1124f26d957388e88cc4990021314b5af247e1d.

* Revert "Revert "FBX settings can be opened again: g_fbxImporter is set, and if the ex… (#878)""

This reverts commit 978477097892a22e83519646527ff52ba6532f35.

* Fixed how FbxImportRequestHandler is loaded

* Bumped version to force FBX to rebuild + removed unused variable

* Revert "Revert "FBX settings can be opened again: g_fbxImporter is set, and if the ex… (#878)""

This reverts commit 978477097892a22e83519646527ff52ba6532f35.

* Revert "Revert "Merge pull request #753 from aws-lumberyard-dev/Helios_DataDrivenAssetImporter""

This reverts commit c1124f26d957388e88cc4990021314b5af247e1d.

* Fixed a bad revert

* Better error reporting at AP launch

* AZ_CRC -> AZ_CRC_CE and removed delayed reload of settings registry file now that it's available at startup

* fixed typo in comment

Code/Sandbox/Plugins/EditorAssetImporter/AssetImporterPlugin.cpp

@@ -14,6 +14,7 @@
 #include <AssetImporterPlugin.h>
 #include <AssetImporterWindow.h>
 #include <QtViewPaneManager.h>
+#include <SceneAPI/SceneCore/Events/AssetImportRequest.h>
 #include <SceneAPI/SceneCore/Utilities/Reporting.h>
 #include <LyViewPaneNames.h>
 #include <AzToolsFramework/API/ToolsApplicationAPI.h>
@@ -37,6 +38,10 @@ AssetImporterPlugin::AssetImporterPlugin(IEditor* editor)
     opt.showInMenu = false; // this view pane is used to display scene settings, but the user never opens it directly through the Tools menu
     opt.saveKeyName = "Scene Settings (PREVIEW)"; // user settings for this pane were originally saved with PREVIEW, so ensure that's how they are loaded as well, even after the PREVIEW is removed from the name
     AzToolsFramework::RegisterViewPane<AssetImporterWindow>(m_toolName.c_str(), LyViewPane::CategoryTools, opt);
+
+    AzToolsFramework::ToolsApplicationRequestBus::Broadcast(
+        &AzToolsFramework::ToolsApplicationRequests::CreateAndAddEntityFromComponentTags,
+        AZStd::vector<AZ::Crc32>({ AZ::SceneAPI::Events::AssetImportRequest::GetAssetImportRequestComponentTag() }), "AssetImportersEntity");
 }
 
 void AssetImporterPlugin::Release()