Update rustup-init to detect tls1.2 for curl 7.73+
Update rustup-init to detect tls1.2 for curl 7.73+

This fixes #2603.  In curl 7.73.0, the help format was changed so as to
only show a summary when calling `curl --help`, while the old menu can
be accessed as `curl --help all`.  This change updates the
`check_help_for` function to detect if the command being checked
contains the curl 7.73.0+ language indicating the use of `--help all`.

If this language is present, `check_help_for` will insert the `all`
category after the `--help` flag, allowing the query to work.  If the
language is not present, then it will insert an empty string following
the `--help` flag, maintaining the same behavior with pre-7.73 versions
of curl.

rust-lang/rustup,nodakai/rustup.rs,nodakai/rustup.rs,rust-lang/rustup,nodakai/rustup.rs,rust-lang/rustup,rust-lang/rustup,nodakai/rustup.rs,nodakai/rustup.rs,rust-lang/rustup