Raise Fd Limit Cli Flag.Fix

A new --raise-fd-limit CLI flag (or VECTOR_RAISE_FD_LIMIT environment variable) raises the file descriptor soft limit to the hard limit at startup. This prevents "Too many open files" errors when Vector monitors large numbers of log files. On macOS, Vector falls back to the kernel-enforced per-process file limit if the hard limit is too high.

authors: vparfonov