User facing:
When a FLUX main model is selected, users may now add Regional Reference Image layers.
When switching between FLUX Redux and FLUX IP Adapter, the settings will change to match the model type. (IP Adapter has weight, begin/end step, but Redux does not.) The image will be retained when switching between the two.
Otherwise it works the same way as IP Adapter - both in Global and Regional Reference Image layers.
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Internal state handling:
Slightly awkward, but it was easiest to make FLUX Redux a second type of IP Adapter in redux state.
Global and regional reference images still have a single `ipAdapter` field, but it can have a type of `ip_adapter` or `flux_redux`.
Ideally, this field is called `config` or `settings` or something, but we are past that point. We _could_ do a migration to rename it, but I don't think it's worth the effort.
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Other changes:
- Updated canvas layer validators to handle FLUX Redux.
- Updated model list loading logic to un-set FLUX Redux models in Canvas if they are not in the list (e.g. if the user deletes the model in the main app).
- Updated graph builders - new `addFLUXRedux` util & updated `addRegions` util.
- Updated the `buildModelsHook` util to return a hook that accepts a filter callback. This handles a discrepancy: FLUX IP Adapter does not support regional guidance, but FLUX Redux does. The Regional Guidance settings provide the filter to filter out FLUX IP Adapter models from the combined list of IP Adapter ahd Redux models.
