fix: automatically create completion for `cargo` and `rustup` plugins (#10087)

plugins/cargo/.gitignore

+_cargo

plugins/cargo/cargo.plugin.zsh

+# COMPLETION FUNCTION
+if (( $+commands[rustup] && $+commands[cargo] )); then
+  if [[ ! -f $ZSH_CACHE_DIR/cargo_version ]] \
+    || [[ "$(cargo --version)" != "$(< "$ZSH_CACHE_DIR/cargo_version")" ]] \
+    || [[ ! -f $ZSH/plugins/cargo/_cargo ]]; then
+    rustup completions zsh cargo > $ZSH/plugins/cargo/_cargo
+    cargo --version > $ZSH_CACHE_DIR/cargo_version
+  fi
+  autoload -Uz _cargo
+  _comps[cargo]=_cargo
+fi

plugins/rustup/.gitignore

+_rustup

plugins/rustup/rustup.plugin.zsh

+# COMPLETION FUNCTION
+if (( $+commands[rustup] )); then
+  if [[ ! -f $ZSH_CACHE_DIR/rustup_version ]] \
+    || [[ "$(rustup --version 2> /dev/null)" \
+      != "$(< "$ZSH_CACHE_DIR/rustup_version")" ]] \
+    || [[ ! -f $ZSH/plugins/rustup/_rustup ]]; then
+    rustup completions zsh > $ZSH/plugins/rustup/_rustup
+    rustup --version 2> /dev/null > $ZSH_CACHE_DIR/rustup_version
+  fi
+  autoload -Uz _rustup
+  _comps[rustup]=_rustup
+fi