Add EXT-CONTROLFLOW and other ranks for COND_IF conditional

Wrap controlflow tests - COND_IF and WHILE_LOOP - in
EXT-CONTROLFLOW extension.
Fix conditional checking for extensions in conformance generation.
Add support for conditional boolean tensor to be rank 0 to 6 instead
of just rank 0 - to match the specification for COND_IF
Add conformance tests to test different ranked conditional tensors.

Signed-off-by: Jeremy Johnson <jeremy.johnson@arm.com>
Change-Id: I0b4739297e054f7c1a5411c551645a9e5b82ebaf