[RegAlloc] Make sure live-ranges reflect the state of the IR when removing them

[RegAlloc] Make sure live-ranges reflect the state of the IR when removing them

When removing a live-range we used to not touch them making debug
prints harder to read because the IR was not matching what the
live-ranges information was saying.

This only affects debug printing and allows to put stronger asserts in
the code (see r308906 for instance).

git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@311401 91177308-0d34-0410-b5e6-96231b3b80d8