[Dispatch Creation] Don't add unfusable consumers to fusion group

[IanWood1]

There are cases where two ops can't be fused as it would result in use-def violation (see the diagram below). Currently, they are still placed in the same fusion group. This means that the consumer gets marked by the analysis as being in a fusion group causing it to potentially miss out on fusion opportunities. This change moves this check so that it occurs during the analysis and modifies the old check to error out.

    A (in fusion group)
    |  \
    |   \
    |    v
    |    B (unfusable consumer of A)
    |   /
    |  /
    v v
    C (trying to fuse with A)

[IanWood1]

Note for reviewers: this checks that hasTransitiveDependencyOnFusionGroup prevents the fusion since the old check will now error out.