Transition QAI8 tests to lazy initialization

This change moves the QAI8 static initializations to lazy, C++17
compliant, initializations. This change also makes use of kernel
interfaces, as to make sure they're exercised

Signed-off-by: Emil Ohlsson <emil.ohlsson@arm.com>

Approved-by: Jens Elofsson <jens.elofsson@arm.com>