* Fix formatting chrono durations to wide strings

* Make format buffers const correct

* Add FormatWide chrono test case

* Fix incorrect wide encoding of 'µs'
I think might be a source file encoding issue, so I used \u00B5 instead.

* Update FormatWide test to use proper encoding of µs

* Revert changes to format_localized's parameters

* Use different overload of `std::time_put<T>::put` to avoid needing a format string

* Use utf8_to_utf16 instead of having redundant overloads of get_units

* Revert some minor changes

* Remove FMT_CONSTEXPR from expression

This should hopefully fix compilation on VS <2019

* Make suggested changes from code review

* Run clang-format on chrono.h

* Make sure unit isn't null before constructing a string_view from it