base: move unique_fd fdsan tests into bionic.

EXPECT_DEATH forks behind the scenes, which turns off fdsan, leading to
these tests failing. Instead of duplicating the special
EXPECT_FDSAN_DEATH macro, just move these tests into the bionic fdsan
tests.

Test: none
Change-Id: Ia7b65d4560601d5a78d143aced887a6773b401c0