IVGCVSW-7889 Add support for Signed64 data type in Cast layer

* Remove mention of "isDepthwise" variable name when not needed and therefore IgnoreUnused call
* Improve error messages and change them to throws in Encoder and Decoder

Signed-off-by: Teresa Charlin <teresa.charlinreyes@arm.com>
Change-Id: I8ce30b5075e1e47d54abc12390265ba8e9ee1405
diff --git a/src/backends/reference/test/RefPerAxisIteratorTests.cpp b/src/backends/reference/test/RefPerAxisIteratorTests.cpp
index 92b828e..d437f4d 100644
--- a/src/backends/reference/test/RefPerAxisIteratorTests.cpp
+++ b/src/backends/reference/test/RefPerAxisIteratorTests.cpp
@@ -5,6 +5,8 @@
 
 #include <reference/workloads/Decoders.hpp>
 
+#include <armnn/utility/IgnoreUnused.hpp>
+
 #include <fmt/format.h>
 
 #include <doctest/doctest.h>