Fixes narrowing conversion build errors in test_common
Removing disable of narrowing errors in main CMakeLists.txt
and moving it down to specific test_conformance suite's
CMakeLists.txt where there are many more build errors revealed
from this fix.
Fixes a few simple issues under test_conformance in the process.
Contributes #787
Signed-off-by: Ellen Norris-Thompson <ellen.norris-thompson@arm.com>
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Signed-off-by: Ellen Norris-Thompson <ellen.norris-thompson@arm.com>
