More features for migration action on morphisms

[kris-brown]

1. As mentioned in the review of Delta migration of acset transformations #710 - it would be nice to have methods for migrating morphisms that presume the dom and codom have already been migrated (to avoid duplicating work when migrating a whole diagram, for example).
2. Other kinds of data migrations (e.g. sigma) should act on morphisms, too.

[ndo885]

Support for handling morphisms in data migration will be very valuable for the use of data migration in our health modeling applications using mappings between model types in StockfFlow.jl and AlgebraicABMs.jl/AlgebraicStatecharts.jl.