Asset Processor: Remove gem loading from AP (#6488)

* AssetBuilder sends builder registration network message to AP

Signed-off-by: amzn-mike <80125227+amzn-mike@users.noreply.github.com>

* Add AP activating status message

Signed-off-by: amzn-mike <80125227+amzn-mike@users.noreply.github.com>

* First builder handles registration.

Fixed deadlock caused by AP and AssetBuilder waiting on each other when registering by moving AP builder start code to a thread

Signed-off-by: amzn-mike <80125227+amzn-mike@users.noreply.github.com>

* Clean up external builder registration

Signed-off-by: amzn-mike <80125227+amzn-mike@users.noreply.github.com>

* Add thread description for builder manager idle thread

Signed-off-by: amzn-mike <80125227+amzn-mike@users.noreply.github.com>

* Remove gem loading

Signed-off-by: amzn-mike <80125227+amzn-mike@users.noreply.github.com>

* Clean up builder registration and remove unused functions

Signed-off-by: amzn-mike <80125227+amzn-mike@users.noreply.github.com>

* Remove PostActivate call from batch application since it will be called after builders are registered

Signed-off-by: amzn-mike <80125227+amzn-mike@users.noreply.github.com>

* Removal external builder dependency scanning since we no longer support builder dlls

Signed-off-by: amzn-mike <80125227+amzn-mike@users.noreply.github.com>

* Fix missing bus disconnect

Signed-off-by: amzn-mike <80125227+amzn-mike@users.noreply.github.com>

* Remove unused variable

Signed-off-by: amzn-mike <80125227+amzn-mike@users.noreply.github.com>

* Moved AP-AssetBuilder specific types into AssetBuilder.Static library.  Also removed some unused/old code

Signed-off-by: amzn-mike <80125227+amzn-mike@users.noreply.github.com>

Code/Tools/AssetProcessor/AssetBuilder/AssetBuilderApplication.cpp

@@ -37,6 +37,7 @@
 #include <AssetBuilderInfo.h>
 #include <AzCore/Interface/Interface.h>
 #include <Entity/EntityUtilityComponent.h>
+#include <AssetBuilderStatic.h>
 
 namespace AssetBuilder
 {
@@ -165,6 +166,7 @@ void AssetBuilderApplication::StartCommon(AZ::Entity* systemEntity)
 
     AssetBuilderSDK::InitializeSerializationContext();
     AssetBuilderSDK::InitializeBehaviorContext();
+    AssetBuilder::InitializeSerializationContext();
     // the asset builder app never writes source files, only assets, so there is no need to do any kind of asset upgrading
     AZ::Data::AssetManager::Instance().SetAssetInfoUpgradingEnabled(false);