COMPMID-3069: Improve build time by splitting up ToolchainSupport.h

Split out the parts of ToolchainSupport coming from <memory> and
the parts coming from <string> into their own new header files.
This accounts for 99% of uses of ToolchainSupport, which means that
expensive header files such as arm_neon.h don't need to be included
everywhere.

Knocks about 10% of compilation time off kernel files.

Signed-off-by: Matthew Bentham <matthew.bentham@arm.com>
Change-Id: I2ae718fe766b5ff28608812b0f686f30eeac1b21
Reviewed-on: https://review.mlplatform.org/c/ml/ComputeLibrary/+/2852
Tested-by: Arm Jenkins <bsgcomp@arm.com>
Reviewed-by: Michele Di Giorgio <michele.digiorgio@arm.com>
diff --git a/src/core/CL/kernels/CLActivationLayerKernel.cpp b/src/core/CL/kernels/CLActivationLayerKernel.cpp
index 3509295..2ab0240 100644
--- a/src/core/CL/kernels/CLActivationLayerKernel.cpp
+++ b/src/core/CL/kernels/CLActivationLayerKernel.cpp
@@ -34,7 +34,7 @@
 #include "arm_compute/core/Utils.h"
 #include "arm_compute/core/Window.h"
 #include "arm_compute/core/utils/helpers/float_ops.h"
-#include "support/ToolchainSupport.h"
+#include "support/StringSupport.h"
 
 #include <cmath>
 #include <set>