Move delegation code out of ISA

[thibault-martinez]

Was put there because we need the issuance but that should be solved later when we have finished the block/tx options refactoring.

[Alex6323]

build_transaction.rs was deleted in #1961, so this issue can be closed?

[thibault-martinez]

It hasn't been deleted, it's been moved. This code still exists in input_selection/requirement/context_inputs.rs so this issue can't be closed.

[Alex6323]

sure, but shouldn't we at least change the title of the issue then?

[thibault-martinez]

We won't do this in the end, it's fine the way it is now.