Add new option to rename eww buffers

Add new option to rename eww buffers

* etc/NEWS: Document the new user options.

* lisp/net/eww.el (eww-auto-rename-buffer, eww-buffer-name-length):
Add new user options.
(eww--rename-buffer): Introduce new function that performs the
renaming of buffers.
(eww--after-page-change): Add new wrapper function which calls
'eww-update-header-line-format' and 'eww--rename-buffer'.
(eww, eww-render, eww-tag-title, eww-readable, eww-restore-history):
Include eww--after-page-change.

Fix bug#51176.

Co-authored-by: Abhiseck Paira <abhiseckpaira@disroot.org>
Co-authored-by: Protesilaos Stavrou <info@protesilaos.com>