[lsan] Be more conservative in SuspendedThreadsListMac::GetRegistersAndSP

Currently, we only return REGISTERS_UNAVAILABLE_FATAL if we receive
KERN_INVALID_ARGUMENT from thread_status. In reality, there are other
possible return values (MACH_SEND_INVALID_DEST for example) that make it
dangerous to read memory. This can be demonstrated by running
create_thread_leak.cpp in standalone mode where it will appear to hang
due to a EXC_BAD_ACCESS while scanning the stack.

This change reverses the current logic to treat MIG_ARRAY_TOO_LARGE as
non-fatal, and all other errors as fatal.

Differential revision: https://reviews.llvm.org/D153072