Fix or move various non-standard tests.

This patch does the following:

* Remove <__config> includes from some container tests.
* Guards uses of std::launch::any in async tests because it's an extension.
* Move "test/std/extensions" to "test/libcxx/extensions"
* Moves various non-standard tests including those in "sequences/vector",
  "std/localization" and "utilities/meta".

llvm-svn: 267981