Fix the virtualization config option 'EnablePushToBackend' to no longer produce submission errors when disabled.

#rb PJ.Kack
#rnx
#jira UE-140366
#preflight 61f2a6f752396dbfeeede332

- Add a way to poll the virtualization system to see if pushing to a backend storage type is possible or not.
- If we cannot push to persistent backend storage when submitting packages to source control we just log in verbose mode and return rather than giving an error. Submitting a non-virtualized package is no longer the problem it once was.

#ROBOMERGE-AUTHOR: paul.chipchase
#ROBOMERGE-SOURCE: CL 18769119 in //UE5/Release-5.0/... via CL 18769125 via CL 18769151
#ROBOMERGE-BOT: UE5 (Release-Engine-Test -> Main) (v903-18687472)

[CL 18769154 by paul chipchase in ue5-main branch]

Engine/Source/Developer/Virtualization/Private/PackageSubmissionChecks.cpp

@@ -142,6 +142,12 @@ void OnPrePackageSubmission(const TArray<FString>& FilesToSubmit, TArray<FText>&
 		return;
 	}
 
+	if (!System.IsPushingEnabled(EStorageType::Persistent))
+	{
+		UE_LOG(LogVirtualization, Verbose, TEXT("Pushing to persistent backend storage is disabled"));
+		return;
+	}
+
 	const double StartTime = FPlatformTime::Seconds();
 
 	// Other systems may have added errors to this array, we need to check so later we can determine if this function added any additional errors.

Engine/Source/Developer/Virtualization/Private/VirtualizationManager.cpp

@@ -288,6 +288,30 @@ bool FVirtualizationManager::IsEnabled() const
 	return !AllBackends.IsEmpty();
 }
 
+bool FVirtualizationManager::IsPushingEnabled(EStorageType StorageType) const
+{
+	if (!bEnablePayloadPushing)
+	{
+		return false;
+	}
+
+	switch (StorageType)
+	{
+		case EStorageType::Local:
+			return !LocalCachableBackends.IsEmpty();
+			break;
+
+		case EStorageType::Persistent:
+			return !PersistentStorageBackends.IsEmpty();
+			break;
+
+		default:
+			checkNoEntry();
+			return false;
+			break;
+	}
+}
+
 bool FVirtualizationManager::PushData(const FPayloadId& Id, const FCompressedBuffer& Payload, EStorageType StorageType, const FString& Context)
 {
 	FPushRequest Request(Id, Payload, Context);

Engine/Source/Developer/Virtualization/Private/VirtualizationManager.h

@@ -92,6 +92,7 @@ private:
 	/* IVirtualizationSystem implementation */
 
 	virtual bool IsEnabled() const override;
+	virtual bool IsPushingEnabled(EStorageType StorageType) const override;
 	
 	virtual bool PushData(const FPayloadId& Id, const FCompressedBuffer& Payload, EStorageType StorageType, const FString& Context) override;
 	virtual bool PushData(TArrayView<FPushRequest> Requests, EStorageType StorageType) override;