IVGCVSW-6311 Add the pre-import backend capability

 * Update acl and ref backend capabilities
 * Add check for AsyncExecution capability in LoadedNetwork
 * Add new exception for capabilities

Signed-off-by: Finn Williams <Finn.Williams@arm.com>
Change-Id: I2f053c845a64f336e96d452793639c6e0d3eaa89
diff --git a/src/backends/reference/RefBackend.hpp b/src/backends/reference/RefBackend.hpp
index 2855957..1a79d70 100644
--- a/src/backends/reference/RefBackend.hpp
+++ b/src/backends/reference/RefBackend.hpp
@@ -13,7 +13,9 @@
                                              {
                                                     {"NonConstWeights", true},
                                                     {"AsyncExecution", true},
-                                                    {"ConstantTensorsAsInputs", true}
+                                                    {"ProtectedContentAllocation", false},
+                                                    {"ConstantTensorsAsInputs", true},
+                                                    {"PreImportIOTensors", false}
                                              });
 
 const std::set<armnn::BackendCapability> oldCpuRefCapabilities {