feat(mise/tools): install Ruby gems with mise

Also remove various old defunct install_*_global_packages helper shell commands.

zsh/rust.zsh

@@ -23,33 +23,8 @@ fi
 
 if command-exists rustup; then
   setup-completions rustup "$(command-path rustup)" rustup completions zsh
-
-  if command-exists cargo; then
-    setup-completions cargo "$(command-path cargo)" rustup completions zsh cargo
-  fi
 fi
 
-# ==============================================================================
-# global rust packages
-# ==============================================================================
-
-install_rust_global_packages() {
-  (
-    set -e
-
-    if ! command-exists rustup; then
-      read -q "REPLY?Rustup was not found. Install it? [y/N] " &&
-        echo &&
-        curl --proto '=https' --tlsv1.2 -sSf https://sh.rustup.rs | sh
-    fi
-
-    if ! command-exists rustup; then
-      echo "Rustup was not found. Aborting."
-      return 1
-    fi
-
-    rustup component add \
-      rust-analyzer \
-      rust-src
-  )
-}
+if command-exists cargo; then
+  setup-completions cargo "$(command-path cargo)" rustup completions zsh cargo
+fi