`ValueMaterializer` is a rewrite of what was called `AdvancedValueInfo`
which follows the same principles.
The main benefits over the old version is:
* We materialize the data-flow graph and the CFG of the relevant part of
root. This makes debugging significantly easier.
* We drop the old MonotoneFramework infrastructure in favor of
getMaximalFixedPoint.
* We significantly reduce the amount of queries we make to
AdvancedValueInfo.
* Assert that the coroutine has reached its final suspension point
when the destructor is called.
* Ensure the move assignment operator takes an rvalue reference.
* Explicitly delete the copy assignment operator.
Alessandro Di Federico