MLECO-3186: Each use case should same namespace convention as KWS and ASR

Certain UCs required additional work due to case context variables which also
became part of a namespace in generated files.
Solution was to declare these extra variables as part of the UC namespace in the respective model.hpp files.
Additional changes to standardise use of namespaces may be required - proposing new task.

Minor typo and rewording of customizing.md in relevant sections included.

Signed-off-by: Liam Barry <liam.barry@arm.com>
Change-Id: Ie78f82a30be252cb841136ea5115f21fc8d762cb
diff --git a/tests/use_case/noise_reduction/RNNoiseModelTests.cc b/tests/use_case/noise_reduction/RNNoiseModelTests.cc
index 9720ba5..7bd83b1 100644
--- a/tests/use_case/noise_reduction/RNNoiseModelTests.cc
+++ b/tests/use_case/noise_reduction/RNNoiseModelTests.cc
@@ -23,14 +23,15 @@
 #include <random>
 
 namespace arm {
-    namespace app {
-        static uint8_t tensorArena[ACTIVATION_BUF_SZ] ACTIVATION_BUF_ATTRIBUTE;
-    } /* namespace app */
+namespace app {
+    static uint8_t tensorArena[ACTIVATION_BUF_SZ] ACTIVATION_BUF_ATTRIBUTE;
+    namespace rnn {
+        extern uint8_t* GetModelPointer();
+        extern size_t GetModelLen();
+    } /* namespace rnn */
+} /* namespace app */
 } /* namespace arm */
 
-extern uint8_t* GetModelPointer();
-extern size_t GetModelLen();
-
 bool RunInference(arm::app::Model& model, std::vector<int8_t> vec,
                     const size_t sizeRequired, const size_t dataInputIndex)
 {
@@ -73,8 +74,8 @@
     REQUIRE_FALSE(model.IsInited());
     REQUIRE(model.Init(arm::app::tensorArena,
                        sizeof(arm::app::tensorArena),
-                       GetModelPointer(),
-                       GetModelLen()));
+                       arm::app::rnn::GetModelPointer(),
+                       arm::app::rnn::GetModelLen()));
     REQUIRE(model.IsInited());
 
     model.ResetGruState();
@@ -128,9 +129,9 @@
 {
     TestRNNoiseModel model{};
     model.Init(arm::app::tensorArena,
-                    sizeof(arm::app::tensorArena),
-                    GetModelPointer(),
-                    GetModelLen());
+               sizeof(arm::app::tensorArena),
+               arm::app::rnn::GetModelPointer(),
+               arm::app::rnn::GetModelLen());
 
     auto map = model.GetStateMap();
 
@@ -152,9 +153,9 @@
 {
     TestRNNoiseModel model{};
     model.Init(arm::app::tensorArena,
-                    sizeof(arm::app::tensorArena),
-                    GetModelPointer(),
-                    GetModelLen());
+               sizeof(arm::app::tensorArena),
+               arm::app::rnn::GetModelPointer(),
+               arm::app::rnn::GetModelLen());
     REQUIRE(RunInferenceRandom(model, 0));
 
     auto map = model.GetStateMap();