refactor: generalize fd/ripgrep vars & options

I intend to eventually replace projectile with project.el, so these
doom-projectile-* variables need to be generalized, starting with the
fd/ripgrep executable paths.

ALong with that, this refactors Doom's projectile-generic-command to
lean more on built-in fd support in projectile, where possible (fewer
wheels reinvented).

Ref: doomemacs/core#1

modules/completion/ivy/config.el

@@ -286,7 +286,7 @@ workable results ripgrep produces, despite the error."
     "Change `counsel-file-jump' to use fd or ripgrep, if they are available."
     :override #'counsel--find-return-list
     (cl-destructuring-bind (find-program . args)
-        (cond ((when-let (fd (executable-find (or doom-projectile-fd-binary "fd") t))
+        (cond ((when-let (fd (executable-find (or doom-fd-executable "fd") t))
                  (append (list fd "--hidden" "--type" "file" "--type" "symlink" "--follow" "--color=never")
                          (cl-loop for dir in projectile-globally-ignored-directories
                                   collect "--exclude"

modules/completion/vertico/autoload/vertico.el

@@ -211,15 +211,15 @@ targets."
 ;;;###autoload
 (defun +vertico/consult-fd-or-find (&optional dir initial)
   "Runs consult-fd if fd version > 8.6.0 exists, consult-find otherwise.
-See URL `https://github.com/minad/consult/issues/770'."
+See minad/consult#770."
   (interactive "P")
   ;; TODO this condition was adapted from a similar one in lisp/doom-projects.el, to be replaced with a more robust check post v3
   (if (when-let*
           ((bin (if (ignore-errors (file-remote-p default-directory nil t))
                     (cl-find-if (doom-rpartial #'executable-find t)
                                 (list "fdfind" "fd"))
-                  doom-projectile-fd-binary))
-           (version (with-memoization doom-projects--fd-version
+                  doom-fd-executable))
+           (version (with-memoization (get 'doom-fd-executable 'version)
                       (cadr (split-string (cdr (doom-call-process bin "--version"))
                                           " " t))))
            ((ignore-errors (version-to-list version))))

modules/emacs/dired/config.el

@@ -211,7 +211,7 @@ we have to clean it up ourselves."
 
 
 (use-package! fd-dired
-  :when doom-projectile-fd-binary
+  :when doom-fd-executable
   :defer t
   :init
   (global-set-key [remap find-dired] #'fd-dired)