Re-commit "Use StringRef in Support/Darf APIs (NFC)"

This reverts commit r283278 and re-commit r283275 with
the update to fix the build on the LLDB side.

git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@283281 91177308-0d34-0410-b5e6-96231b3b80d8
11 files changed