Allow for folly::exception_wrapper in ClientReceiveState

Allow for folly::exception_wrapper in ClientReceiveState

Summary:
This diff allows us to use folly::exception_wrapper in ClientReceiveState. Existing use cases are still supported (crs.exception() still returns an exception_ptr no matter what), but we can now choose to set an exception without throwing first.

On the folly side, add some new functions for making an exception_ptr from an exception_wrapper.

Test Plan: Reran unit tests

Reviewed By: davejwatson@fb.com

FB internal diff: D1307027

@override-unit-failures