Fixes for Try::withException

Fixes for Try::withException

Summary:
[Folly] Fixes for `Try::withException`.

* Fix the overload with the exception type specified so that the specified exception type is checked. A mismatch between the specified exception type and the parameter type of the passed invokable will result in the expected compiler error.
* Add an overload where the exception type is deduced intentionally, as opposed to accidentally.

Of course, these simply forward to their corresponding `exception_wrapper::withException` overloads.

Reviewed By: ericniebler

Differential Revision: D5216691

fbshipit-source-id: 7e85c906c3aa17dfede6e0980c6ac8bf75034073