[CK_BUILDER] Support multi-A/B/D tests #4967

Problem

In the current implementation of CK-Builder's testing mechanism, support for multiple A/B/D tensors is omitted. These inputs can be described in the signature, there is just currently no mechanism to supply those inputs or to wire them up to the backing implementation. This issue relates to #4965, I think it wouldn't make sense to start on this before clearing up that one.

There are multiple aspects to this issue (feel free to split it further up into sub-tasks, that should be quite easy):

1. The Inputs and Outputs structures currently have the list of tensors hardcoded to just the "main" ones: For example, for forward, input/weight for the Inputs type and output for the Outputs type. This should be adapted to the full list of multi-A/B/D tensors specified in the signature, probably to be extracted using some metaprogramming.
2. ckt::run() plumbing for these.
3. ckt::init_inputs() will need to also be extended, for multi-A/B.
4. ckt::validate() might need to be extended, unless reflect() is properly implemented.
5. The reference implementation might need to be extended with support for multi-A/B/D.