Standardize and promote c-ts-mode's custom matcher and anchor

Standardize and promote c-ts-mode's custom matcher and anchor

Specifically, standalone-parent and prev-sibling.  The c-ts-mode
custom version skips labels and proproc directives.

* lisp/progmodes/c-ts-mode.el:
(c-ts-mode--standalone-parent-skip-preproc): Rename to
c-ts-mode--standalone-parent, and make it skip labels too.
(c-ts-mode--preproc-indent-rules): Rename standalone-parent and
prev-sibling.
(c-ts-mode--label-indent-rules): Use custom standalone-parent
and prev-sibling.

(cherry picked from commit 9acf6eff01a82c3fe9ca8897f38b76dbb6079648)