Introduce the `makeGotoEdge` helper to the `ScopeGraphBuilder` class,
that can be used to handle the transformation of a solid edge into a
`goto` edge, taking care of the creation of the `goto` block and the
redirection of the edges.
Do not assert if the marker function is not present in the input IR, the
`Builder` instantiation takes care of its on-the-fly declaration
instantiation.
Introduce the `ScopeCloser` and `GotoTarget` annotations in the IR, and
the relative necessary machinery, needed to handle scope closer and goto
edges for the new backend.
A specialization of the `llvm::GraphTraits`, called `ScopeGraph`, that
is able to handle both the above mentioned annotations is provided.
For the `llvm::GraphTraits` implementation, we introduce the
`GeneratorIterator` class, which uses a coroutine to store the status of
the iteration.
A debug logger pass is added, so that we are able to test the
functionality with `FileCheck`.
Andrea Gussoni