IVGCVSW-4860 Add tests to verify QLstm projection

* Adds int16 output tensor to CpuRef impl to
  prevent overflow when accumulating output
  after projection.
* Adds two remaining tests to verify QLstm on
  CpuRef.

Signed-off-by: James Conroy <james.conroy@arm.com>
Change-Id: I93d7c64c4a9cc1012cb2bc052d598d4279fbd372
diff --git a/src/backends/backendsCommon/test/layerTests/LstmTestImpl.hpp b/src/backends/backendsCommon/test/layerTests/LstmTestImpl.hpp
index f1180ae..6e29345 100644
--- a/src/backends/backendsCommon/test/layerTests/LstmTestImpl.hpp
+++ b/src/backends/backendsCommon/test/layerTests/LstmTestImpl.hpp
@@ -66,3 +66,11 @@
 LayerTestResult<int8_t, 2> QLstmTest(
     armnn::IWorkloadFactory& workloadFactory,
     const armnn::IBackendInternal::IMemoryManagerSharedPtr& memoryManager);
+
+LayerTestResult<int8_t, 2> QLstmTest1(
+    armnn::IWorkloadFactory& workloadFactory,
+    const armnn::IBackendInternal::IMemoryManagerSharedPtr& memoryManager);
+
+LayerTestResult<int8_t, 2> QLstmTest2(
+    armnn::IWorkloadFactory& workloadFactory,
+    const armnn::IBackendInternal::IMemoryManagerSharedPtr& memoryManager);
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