Suggestion: rename `--ignore-failure` to `--ignore-exit-code` for Hyperfine 2.0

[ilyagr]

To me, --ignore-failure suggests one the behaviors I asked for in #827, ignoring the measurements for the failed runs. However, actually the option makes it so that hyperfine considers all runs successful, regardless of the exit code.

So, I think --ignore-exit-code would be a better name.