Since the introduction of "ColumnLimit: 120" in .clang-format, the
column limit has become 120 characters instead of 80 characters.
This prevents clang-format from generating too much changes even if just
a small portion of a source file or header file is modified.
1. Normalize paths in LSP document URIs and project root to forward
slash and uppercase drive letters.
2. Normalize paths in compile_commands.json to forward slash and
uppercase drive letters.
3. Normalize paths from directory listing to forward slash. (Drive
letter should be same as input dir path, which is already uppercase
since path of project root dir is normalized)
4. Add llvm::sys::path::convert_to_slash after certain llvm::sys::path
and llvm::fs calls.
