elisp--xref-find-definitions handle cl-defstuct default constructor

elisp--xref-find-definitions handle cl-defstuct default constructor

* lisp/progmodes/elisp-mode.el (elisp-xref-find): Add FIXME.
(elisp--xref-format-extra): Rename from elisp--xref-format-cl-defmethod.
(elisp--xref-find-definitions): Handle cl-defstuct default constructor.

* test/automated/elisp-mode-tests.el (xref-elisp-test-run): Split out
from xref-elisp-test for ease of debugging.
(xref-elisp-deftest): Rename from xref-elisp-test.
(find-defs-constructor): New test.
(find-defs-defgeneric-el): Match batch test config.
(compile): Required for find-defs compilation-minor-mode test.
(find-defs-defvar-el): Match code change.
(find-defs-face-el): Match code change.

* lisp/progmodes/xref.el (xref-find-function, xref-find-definitions):
Improve doc string.