Rename `file-attribute-file-number' to `file-attribute-file-identifier'

Rename `file-attribute-file-number' to `file-attribute-file-identifier'

* doc/lispref/files.texi (File Attributes):
* etc/NEWS:
* lisp/files.el (find-buffer-visiting, find-file-noselect)
(set-visited-file-name, basic-save-buffer)
(file-attribute-file-identifier):
* lisp/startup.el (normal-top-level-add-subdirs-to-load-path):
* lisp/eshell/em-unix.el (eshell-shuffle-files):
* src/dired.c (Ffile_attributes):
Rename `file-attribute-file-number' to `file-attribute-file-identifier'.