If it is smaller than 500 * (Maximum number of threads), the method reverts to the original
unthreaded version of the function. This old function is also the one used if the input
array has random access iterators.

This should fix slow python.api tests and hopefully should get rid of the timeouts on build servers.

Update to clang-format-5 and reformat the codebase 

This was a request after seeing #23083.

This will allow users to have logging again

MSVC 2017 15.7 contains a bug where constant initialization no longer
takes place for objects with constructors marked constexpr such as
once_flag. This leaves once_flag susceptible to dynamic initialization
order problems and causes some singleton instances to be constructed
incorrectly. We put back our correct implementation (with some cleanup)
and await a fix from MS.
Refs #0

and improve the default user properties file.

re #23102

re #23102

re #23102

re #23102