This PR splits up the SCC that the compiler manages into (potentially)
multiple ones after
performing lambda lifting. This aids both the closed term extractor and
the elimDeadBranches pass as
they are both negatively influenced when more declarations than required
are within one SCC.
This PR removes the old ElimDeadBranches pass and shifts the new one
past lambda lifting.
The reason for dropping the old one is its general unsoundness and the
fact that we want to do refactorings on the IR part. The reason for
shifting the current pass past lambda lifting, is that its analysis is
imprecise in the presence of local function symbols. I experimented with
the exact placement for a while and it seems like it is optimal here.
Overall we observe a slight regression in the amount of C code
generated, likely because we don't propagate information into lambdas
before lifting them anymore. But generally measure a slight performance
improvement in general.
