test(cts): Update regions and indexing structure

Both binary and constant COND_IF tests have been updated to match the serialization library spec.

• then_block and else_block are now in separate, corresponding regions
• Lazy data generation has been disabled for the operator
• Support for the old, single region format has been removed and will now cause the reference model to error

The TosaSerializer has been updated to track names of inputs, constants and layers globally, instead of per region, using the IndexCounter class.

• Tests have been added to monitor expected indexing
• Python bindings have also been updated to match the python API

Note: the original index structure has been retained to account for unexpected uses of the API, but will be removed in a later release.

Signed-off-by: Madeleine Dunn madeleine.dunn@arm.com