Add :tools lsp checks for +lsp flag

Also:
- Reorganizes some :lang modules' packages.el file.
- Adds setuptools check in lang/python
- Adds javac check in lang/java
- Removes the depends-on! macro

modules/lang/rust/doctor.el

@@ -1,6 +1,16 @@
 ;; -*- lexical-binding: t; no-byte-compile: t; -*-
 ;;; lang/rust/doctor.el
 
+(assert! (or (not (featurep! +lsp))
+             (featurep! :tools lsp))
+         "This module requires (:tools lsp)")
+
+(unless (executable-find "rust")
+  (warn! "Couldn't find rust binary"))
+
+(unless (executable-find "cargo")
+  (warn! "Couldn't find cargo binary"))
+
 (when (require 'racer nil t)
   ;; racer
   (unless (file-exists-p racer-cmd)

modules/lang/rust/packages.el

@@ -1,8 +1,6 @@
 ;; -*- no-byte-compile: t; -*-
 ;;; lang/rust/packages.el
 
-;; requires rust cargo racer
-
 (package! rust-mode)
 
 (when (featurep! :tools flycheck)