Implements a -- delimiter, that indicates the end of options (starting
with a dash -) of a command and separates them from the subsequent
operands (positional arguments).
The following commands are affected:
- env: Implemented the -- delimiter.
- cat: The -- delimiter was already kind of considered, but its
occurence did not stop the options parsing.
- rm: Here the command already implemented the -- delimiter as
specified, but it was not documented.
Fixes#22970