Document tree-sitter features in the user manual

Document tree-sitter features in the user manual

* lisp/progmodes/c-ts-mode.el (c-ts-mode-map): Bind "C-c .", for
consistency with CC mode.
* lisp/treesit.el (treesit-font-lock-level): Doc fix.

* doc/emacs/programs.texi (C Indent, Custom C Indent): Document
the indentation features of 'c-ts-mode'.
(Moving by Defuns): Document 'treesit-defun-tactic'.
* doc/emacs/files.texi (Visiting): Document
'treesit-max-buffer-size'.
* doc/emacs/display.texi (Traditional Font Lock)
(Parser-based Font Lock): New subsections.
* doc/emacs/emacs.texi (Top): Update top-level menu.