Move CCC_OVERRIDE_OPTIONS support to clangDriver so that it may be used outside of the clang driver binary. The override functionality will be used in LLDB, to apply adjustments to ClangImporter flags. This will be useful as an escape hatch when there are issues that can be fixed by adding or removing clang flags. The only thing changed is the name, from `ApplyQAOverride` to `applyOverrideOptions`.