[Test] Gave async/partial_apply[_forwarder].sil pa'd funcs sizes.

Previously, the partially applied functions were not defined and as such
had no sizes.  That resulted in downstream issues as an attempt was made
to replace the size in the AsyncFunctionPointer for the functions'
forwarders with the size in the AsyncFunctionPointer for functions
because the latter did not exist.

Author: nate-chandler