[CodeView] Use llvm::Error instead of std::error_code.

This eliminates the remnants of std::error_code from the
DebugInfo libraries.

git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@277758 91177308-0d34-0410-b5e6-96231b3b80d8
9 files changed