Add full rank coverage for fp8 CONST

Add CTS tests to cover ranks 0, 4, 5, and 6 for fp8e4m3 and fp8e5m2
which were previously lacking.

Signed-off-by: Ian Tayler Lessa <ian.taylerlessa@arm.com>
Change-Id: I594b651cf7fedd70d91d3e79f83cf84ec1b552ef