Adjust the JVM heap size with the `rss_limit_mb`

[fmeum]

Do we want to adjust the JVM heap size with the rss_limit_mb value set by the user?

I thought about this as well, but are users more likely to change rss_limit_mb or -Xmx via jvm_args? I would have guessed the latter, but am not sure. We would probably have to parse both and warn if they conflict, but that requires quite a bit of logic. What do you think?

Originally posted by @fmeum in https://github.com/CodeIntelligenceTesting/jazzer/issues/93#issuecomment-834127882