Revert "[CodeView] Provide a common interface for type collections."

This is a squash of ~5 reverts of, well, pretty much everything
I did today.  Something is seriously broken with lit on Windows
right now, and as a result assertions that fire in tests are
triggering failures.  I've been breaking non-Windows bots all
day which has seriously confused me because all my tests have
been passing, and after running lit with -a to view the output
even on successful runs, I find out that the tool is crashing
and yet lit is still reporting it as a success!

At this point I don't even know where to start, so rather than
leave the tree broken for who knows how long, I will get this
back to green, and then once lit is fixed on Windows, hopefully
hopefully fix the remaining set of problems for real.

llvm-svn: 303409