Add /proc/[pid]/cmdline support

[StanPlatinum]

No description provided.

[liqinggd]

Please see this commit 09deddb to implement the proc/pid/cmdline

[StanPlatinum]

Please see this commit 09deddb to implement the proc/pid/cmdline

Thanks @liqinggd ! I adopted your code and made a minor modification, which is more suitable and accurate using argv() to get the cmdline.

        let cmdline_output = if self.0.is_zombie() {
            // Returns 0 characters for zombie process.
            Vec::new()
        } else {
            let Ok(argv_cstrs) = self.0.vm().init_stack_reader().argv() else {
                return Ok(Vec::new());
            };
            argv_cstrs
                .into_iter()
                .flat_map(|c_str| c_str.into_bytes_with_nul().into_iter())
                .collect()
        };
        Ok(cmdline_output)

[liqinggd]

LGTM

[tatetian]

LGTM. Thanks for the contribution!