[GWP-ASan] Enable backtrace/enable_disable/iterate tests.

Enable the enable_disable & iterate tests on Android. These work out of
the box.

Also enable the backtrace test. This requires some extra interfacing
with libunwindstack, but that's all wrapped up now.

Bug: 152414185
Test: SANITIZE_TARGET=hwaddress atest gwp_asan_unittest
Change-Id: Ie02f8fdcb28b4324f07517874b45996e0b59c8df
3 files changed