Re-architecture staging phase and fix all known issues of that phase#8796

Merged

nicolasstucki merged 2 commits intoscala:masterfrom

dotty-staging:reimplement-staging-phase

May 5, 2020

Commits on May 4, 2020

Re-architecture the staging phase.
nicolasstucki
committed

Commits on May 5, 2020

Fix typos
nicolasstucki
committed