Unbreak Eglot, Jsonrpc as EIEIO inches closer to CLOS (bug#67480)

Unbreak Eglot, Jsonrpc as EIEIO inches closer to CLOS (bug#67480)

EIEIO is an innacurate emulation of CLOS in many aspects and one of
them in accessor definition.  Before this commit

commit 6c47931a1ad4de4af3f147b9604169c2441100fe
Author: Brandon <brandon.irizarry@gmail.com>
Date:   Sat Nov 4 17:11:32 2023 -0400

    Make EIEIO ':accessor' behave like ':reader' when reading (bug#66938)

An :initform-less, non-:initarg'ed slot with be read using an
:accessor which would just return nil.  This is EIEIO specific of
course, but it made for (my) sloppy programming in jsonrpc.el and
eglot.el.

Tightening up the rules a bit meant these things broke and now I'm
fixing them.

* lisp/jsonrpc.el (jsonrpc-connection): Add a bunch of :initform nil
(jsonrpc-process-connection): Add a bunch of :initform nil

* lisp/progmodes/eglot.el (eglot-lsp-server): Add a bunch of :initform nil