[PECOFF] Convert more binary files to YAML.

Because the object files are now readable to humans, I don't think we need the
source assembly file any more, so I removed them too in this commit.

git-svn-id: https://llvm.org/svn/llvm-project/lld/trunk@200276 91177308-0d34-0410-b5e6-96231b3b80d8