[libc][test] `atan*` and `smoke/atan*` tests need to have exception and errno checking fixed

[Flandini]

These depends on ASSERT_GE and EXPECT_GE in {ASSERT,EXPECT}_FP_EXCEPTION. Using RoundingMode with the quick rounding mode tests ends up setting exceptions, so after switching these to {ASSERT,EXPECT}_EQ, these tests are failing and need to be changed to wrap the function invocation and not the entire RoundingMode test setup.

See #88816