bug#56407: 29.0.50; desktop.el shouldn't be saving/restoring eglot--managed-mode, which is not for interactive use

[Eli Zaretskii <eliz@gnu.org>]

> From: João Távora <joaotavora@gmail.com>
> Date: Wed, 6 Jul 2022 13:59:51 +0100
> Cc: 56407@debbugs.gnu.org
> 
>  That's okay: it's desktop.el's job to know about some implementation
>  details.  Just look at how much it knows about what the various modes
>  and variables do in Emacs.
> 
> Wait, you're saying it's "okay" to have to do a commit to Emacs's repo 
> everytime someone makes a third-party package that has a minor mode 
> that needs special handling?  Or everytime someone changes the name
> or shape of a minor mode?

eglot is not a third-party package.  We intended to add it to core, I
think?

But if what I suggest isn't to your liking, you can always tell users
to customize desktop-minor-mode-table by themselves.  Or do what you
didn't want to do: cause desktop.el to be autoloaded by eglot.

> But we do have that mechanism. It's called symbol properties and it's a nice
> feature of lisp. So let's use it, please.

If you insist.  But then don't come back crying when this is broken by
some change in desktop.el that the "loosely coupled packages" didn't
pick up.