[PM][CGSCC] Add a helper to update the call graph from SCC passes

With this patch new trivial edges can be added to an SCC in a CGSCC
pass via the updateCGAndAnalysisManagerForCGSCCPass method. It shares
almost all the code with the existing
updateCGAndAnalysisManagerForFunctionPass method but it implements the
first step towards the TODOs.

This was initially part of D70927.

Reviewed By: JonChesterfield

Differential Revision: https://reviews.llvm.org/D72025