[libc++][hardening] XFAIL test in fast mode under HWASAN (#78862)

After #77883, `fast` mode uses TRAP, and HWASAN
replaces TRAP with abort or error exit code.

On a quick looks it should be possible to avoid doing
that in HWASAN, but historically this is convention for all
sanitizers. Changing this behavior may break existing
users.

Other sanitizers are not affected because they don't
install TRAP handlers by default. But if they do, they also
replace TRAP with abort/exit.