Make EIEIO use records.

Make EIEIO use records.

* lisp/emacs-lisp/eieio-compat.el
(eieio--generic-static-object-generalizer): Adjust to new tags.

* lisp/emacs-lisp/eieio-core.el: Use records, and place the class object
directly as tag.
(eieio--object-class): Adjust to new tag representation.
(eieio-object-p): Rewrite, and adapt to new `type-of' behavior.
(eieio-defclass-internal): Use `make-record'.
(eieio--generic-generalizer): Adjust generalizer code accordingly.

* lisp/emacs-lisp/eieio.el (make-instance, clone): Use copy-record.

* lisp/emacs-lisp/pcase.el (pcase-mutually-exclusive-predicates):
Add `recordp'.

* doc/lispref/records.texi, doc/misc/eieio.texi: Update for records.