test(cts): Generalise getRandomTensorData to ints
This allows us to also generate int32_t, int16_t and int8_t tensors with the same function. It moves the code to test_utils.h so that it can be used outside of verify_tests.cpp.
Also adds one verify test for exact mode with int8_t, using the int specialisation of getRandomTensorData.
Signed-off-by: Ian Tayler Lessa ian.taylerlessa@arm.com