Summary:
Suspending the coroutine before it's destroyed prevents a dangling
reference to its value.

This dangling reference is exposed when running tests that were
built with `-O3` with ASAN. To run tests at this level, split the
tests up: move tests that cannot be compiled with ASAN at `-O3`,
due to https://bugs.llvm.org/show_bug.cgi?id=34289, into their
own file. The remaining tests stay where they are, with `-O3`
re-enabled.

Reviewed By: yfeldblum

Differential Revision: D7130814

fbshipit-source-id: bf3e2b8f4a086f1786ab46f453c3dd9171d018e8