Add a .clang-format file to WIL

[dunhor]

Previous draft PR was here: https://github.com/microsoft/wil/pull/401, which has a few comments. I've created a new one as that one had a bit of experimentation and got a little messy. The biggest topic of conversation from before was the outer-most namespace contents not getting tabbed causing a lot of whitespace changes. For now the plan is to roll with it, however that may make merge conflicts a little tricky in the short term.

NOTE: The .clang-format file has been take from the OS repo with very minimal additions to ensure that some of WIL's macros don't cause weird formatting. This is not a request for comment on personal style preferences. Comments and feedback should be focused on issues with the formatting (e.g. macros being handled incorrectly, etc.).

For now, all I've done is add the .clang-format (with additions mentioned above), add a script that runs clang-format over all our code with the version of clang-format that ships with Visual Studio (as an attempt to get some consistency), and then run said script. No manual code changes have been made (I'll call out any I end up making). A few things I plan to look into for the future:

• PR validation that either fails if clang-format was not run, or just runs clang-format and submits the result. For now, we can ask people to run clang-format if it's obvious that they didn't, but otherwise just run it ourselves periodically (likely on an OS sync)l
• A script to just format lines that have changed (from my understanding there's some degree of git integration with clang-format)

A few additional things I plan to address/look into:

• C++/CX "hat" (^) pointers get formatted like they are XOR operations. I plan to do a global search for __cplusplus_winrt and wrap them with clang-format off/clang-format on and fix the pointer formatting. That way the code is still formatted initially, but will require manual intervention in the future
• Exclude the workarounds directory from auto-formatting
• Some very long template <...> lines seem to not be getting wrapped (though others are for some reason). I plan to investigate those
• The following macros/non-standard compiler extensions seem to sometimes cause issues; I plan to look at these, but not quite sure what/how much I can fix:
  • Use of __R* macros in result_macros.h sometimes cause line breaks, sometimes not
  • Some function definitions that have RESULT_NORETURN/__declspec(noinline) sometimes get formatted weirdly
  • Use of SAL annotations seem to be correlated with some inconsistent formatting
  • Macros that specify function names (e.g. something like #define FUNCTION(ret, name) ...) sometimes gets formatted weirdly

A few additional notes/questions:

• WI_NOEXCEPT sometimes causes interesting formatting side effects. In particular, on constructors that contain initializers and functions with trailing return types (e.g. auto fn() WI_NOEXCEPT -> int) where the -> gets formatted like a pointer access. There's a way to tell clang-format that this is a macro for noexcept which fixes the formatting, however it's relatively new and the version of clang-format that ships with Visual Studio does not include it.
• There's a decent amount of macro churn in both result_macros.h and tracelogging.h that doesn't necessarily make the code easier to read/understand. Are there any places where we want to disable formatting in those files?

[dunhor]

I don't have strong opinions about the questions you asked in the PR description. do what you think is best.

I found some annotations that were missing. Otherwise, couldn't figure out any non-hacky way to get the rest to work. The Macros vector seems to work decently well, but isn't available until version 17, which is higher than the version that ships with VS. I'll delay those for now. I'll leave everything else as-is. We can go back and re/un-format if we get too annoyed with it later