test(complete): Include a visible command alias

Only zsh includes completion for visible aliases of subcommands. Let's
show that in tests.

clap_complete/tests/common.rs

@@ -151,6 +151,7 @@ pub fn sub_subcommands_command(name: &'static str) -> clap::Command {
     feature_sample_command(name).subcommand(
         clap::Command::new("some_cmd")
             .about("top level subcommand")
+            .visible_alias("some_cmd_alias")
             .subcommand(
                 clap::Command::new("sub_cmd").about("sub-subcommand").arg(
                     clap::Arg::new("config")

clap_complete/tests/snapshots/sub_subcommands.zsh

@@ -151,6 +151,7 @@ _my-app_commands() {
     local commands; commands=(
 'test:tests things' \
 'some_cmd:top level subcommand' \
+'some_cmd_alias:top level subcommand' \
 'help:Print this message or the help of the given subcommand(s)' \
     )
     _describe -t commands 'my-app commands' commands "$@"