COMPMID-1283: (GitHub issue) after convolution output data is zero

During the mutating passes accessors of optimized nodes were dropped
instead of being transfered to appropriate tensors.

Change-Id: I29183984d94806bdfb5c92af3acefd928c0fd171
Reviewed-on: https://eu-gerrit-1.euhpc.arm.com/136036
Reviewed-by: Anthony Barbier <anthony.barbier@arm.com>
Tested-by: Jenkins <bsgcomp@arm.com>
diff --git a/arm_compute/graph/Tensor.h b/arm_compute/graph/Tensor.h
index 5199ac2..54fb258 100644
--- a/arm_compute/graph/Tensor.h
+++ b/arm_compute/graph/Tensor.h
@@ -82,6 +82,13 @@
      * @return Backend tensor accessor
      */
     ITensorAccessor *accessor();
+    /** Extracts accessor from the tensor
+     *
+     * @warning Accessor gets unbound from the tensor
+     *
+     * @return The accessor of the tensor
+     */
+    std::unique_ptr<ITensorAccessor> extract_accessor();
     /** Calls accessor on tensor
      *
      * @return True if the accessor was called else false