Golang: add rsync as a program capable of arbitrary shell command execution

[pwntester]

Add rsync since both --rsh and --rsync-path admit commands

[smowton]

@pwntester please rebase so we only get one commit instead of a big merge. I think this would also be sensible to add to override predicate doubleDashIsSanitizing() in SystemCommandExecutors.qll, since I think "rsync ... -- " + userData would be as safe as letting someone control an rsync could ever be?

[smowton]

Please add a test case to https://github.com/github/codeql/tree/main/go/ql/test/query-tests/Security/CWE-078 too

[pwntester]

@smowton let me know if it looks better now. Would it make sense to share these lists of commands with other languages in a shared qlpack or similar?

[smowton]

Wants a change-note, otherwise looks good

[owen-mc]

@pwntester The tests are failing because it doesn't like your declaration of a function namedhandler - there's already one in another file in the same folder. Also you need to rebase your branch onto main.