Use UTF-8 for communication with clang-format and convert the
replacements offset/length to characters position/count.
Internally VisualStudio.Text.Editor.IWpfTextView use sequence of Unicode
characters encoded using UTF-16 and use characters position/count for
manipulating text.
Resolved "Error while running clang-format: Specified argument was out
of the range of valid values. Parameter name: replaceSpan".
Patch by empty2fill!
Differential revision: https://reviews.llvm.org/D70633
e20a1e486e