Reconsider `build`/`finish` for Builders with conditions

[grtlr]

Some of our current builders don't enforce the conditions of the underlying type at compile-time but rather check for it during construction at runtime.

An example of this is AliasOutputBuilder. One way to mitigate this is to add the two UnlockConditions as parameters to finish.

Maybe we can do this as part of #1024.