Store anchors option for supported output types

Store anchors option for supported output types

As we integrate the support of anchor outputs, we'll want to know if
each input we're working with came from an anchor outputs channel.
Instead of threading through a `opt_anchors` boolean across several
methods on `PackageSolvingData` and `PackageTemplate`, we decide to
store a reference in each `PackageSolvingData` variant instead that
features a change in behavior between channels with and without anchor
outputs.