Add extra line before repro log; update repro log tests

[yf225]

In the log, sometimes the first line of the repro script # === HELION KERNEL REPRO === is in the same line with some prefix, like:

WARNING:helion.runtime.kernel:# === HELION KERNEL REPRO ===
import helion
import helion.language as hl
import torch
from torch._dynamo.testing import rand_strided
...

which requires work from the user to remove the prefix to make the script runnable (e.g. #1081). This PR logs a new line before logging the repro script, so that it's easier to copy-paste a working repro script.