Make session persistence module agnostic

They've been removed from feature/workspaces and moved into
core/autoload/sessions, which falls back to desktop.el if persp-mode
isn't present. This also offers a substantial speed up to
restart+restoring and restoring sessions in general.

Also fixes #1210, where the newly spawned frame after doom/restart
wasn't focused.

Introduces the following commands:

- doom/restart
- doom/restart-and-restore
- doom/quickload-session
- doom/quicksave-session
- doom/load-session
- doom/save-session
- +workspace/restore-last-session (alias for doom/quickload-session)

And removes

- +workspace/load-session
- +workspace/save-session
- +workspace/load-last-session (renamed to +workspace/restore-last-session)
- +workspace/restart-emacs-then-restore (replaced by doom/restart-and-restore)
- :ss (ex command)
- :sl (ex command)

modules/feature/workspaces/autoload/workspaces.el

@@ -112,14 +112,6 @@ Returns t if successful, nil otherwise."
    *persp-hash* (list name))
   (+workspace-exists-p name))
 
-;;;###autoload
-(defun +workspace-load-session (&optional name)
-  "Replace current session with the entire session named NAME. If NAME is nil,
-use `persp-auto-save-fname'."
-  (mapc #'+workspace-delete (+workspace-list-names))
-  (persp-load-state-from-file
-   (expand-file-name (or name persp-auto-save-fname) persp-save-dir)))
-
 ;;;###autoload
 (defun +workspace-save (name)
   "Saves a single workspace (NAME) from the current session. Can be loaded again
@@ -134,18 +126,6 @@ Returns t on success, nil otherwise."
     (and (member name (persp-list-persp-names-in-file fname))
          t)))
 
-;;;###autoload
-(defun +workspace-save-session (&optional name)
-  "Save a whole session as NAME. If NAME is nil, use `persp-auto-save-fname'.
-Return t on success, nil otherwise."
-  (let ((fname (expand-file-name (or name persp-auto-save-fname)
-                                 persp-save-dir)))
-    ;; disable auto-saving on kill-emacs if autosaving (i.e. name is nil)
-    (when (or (not name)
-              (string= name persp-auto-save-fname))
-      (setq persp-auto-save-opt 0))
-    (and (persp-save-state-to-file fname) t)))
-
 ;;;###autoload
 (defun +workspace-new (name)
   "Create a new workspace named NAME. If one already exists, return nil.
@@ -206,6 +186,9 @@ throws an error."
 ;;
 ;; Commands
 
+;;;###autoload
+(defalias '+workspace/restore-last-session #'doom/quickload-session)
+
 ;;;###autoload
 (defun +workspace/load (name)
   "Load a workspace and switch to it. If called with C-u, try to reload the
@@ -236,46 +219,6 @@ workspace."
       (+workspace-message (format "'%s' workspace saved" name) 'success)
     (+workspace-error (format "Couldn't save workspace %s" name))))
 
-;;;###autoload
-(defun +workspace/load-session (&optional name)
-  "Load a session and switch to it. If called with C-u, try to load the last
-session."
-  (interactive
-   (list
-    (unless current-prefix-arg
-      (completing-read
-       "Session to load: "
-       (directory-files persp-save-dir nil "^[^_.]")
-       nil t))))
-  (condition-case ex
-      (let ((name (or name persp-auto-save-fname)))
-        (+workspace-load-session name)
-        (+workspace-message (format "'%s' workspace loaded" name) 'success))
-    '(error (+workspace-error (cadr ex) t))))
-
-;;;###autoload
-(defun +workspace/load-last-session ()
-  "Restore last session and switch to it."
-  (interactive)
-  (+workspace/load-session))
-
-;;;###autoload
-(defun +workspace/save-session (&optional name)
-  "Save the current session. If called with C-u, prompt you for the name to save
-the session as."
-  (interactive
-   (list
-    (when current-prefix-arg
-      (completing-read
-       "Save session as: "
-       (directory-files persp-save-dir nil "^[^_.]")))))
-  (condition-case-unless-debug ex
-      (let ((name (or name persp-auto-save-fname)))
-        (if (+workspace-save-session name)
-            (+workspace-message (format "Saved session as '%s'" name) 'success)
-          (error "Couldn't save session as '%s'" name)))
-    ('error (+workspace-error ex t))))
-
 ;;;###autoload
 (defun +workspace/rename (new-name)
   "Rename the current workspace."
@@ -437,12 +380,6 @@ the next."
 
               (t (+workspace-error "Can't delete last workspace" t)))))))
 
-;;;###autoload
-(defun +workspace/restart-emacs-then-restore ()
-  "Restarts Emacs, then restores the session."
-  (interactive)
-  (restart-emacs (list "--restore")))
-
 
 ;;
 ;; Tabs display in minibuffer