Expose sendUnsigned; move sending functions to Amazonka.Send and re-export

[endgame]

In the current layout, a function like sendUnsigned (if you can forgive the bikeshedding/renaming) would live in the root Amazonka module, but if you do this you will create an import loop. Maybe create an Amazonka.Send module which can hold send/sendEither/paginate/paginateEither/sendUnsigned/sendUnsignedEither and ensure these functions are re-exported by the Amazonka module?

Originally posted by @endgame in #757 (comment)