Use 'char-to-name'

* lisp/international/emoji.el (emoji--name): Lookup name using 'char-to-name'.
* lisp/international/textsec.el (textsec-domain-suspicious-p): And here.
* lisp/simple.el (what-cursor-position): And here.

lisp/international/emoji.el

@@ -245,7 +245,7 @@ the name is not known."
 
 (defun emoji--name (glyph)
   (or (gethash glyph emoji--names)
-      (get-char-code-property (aref glyph 0) 'name)))
+      (char-to-name (aref glyph 0))))
 
 (defvar-keymap emoji-list-mode-map
   "RET" #'emoji-list-select

lisp/international/textsec.el

@@ -296,7 +296,7 @@ or use certain other unusual mixtures of characters."
                             ""
                           (concat ": " (string char)))
                         char
-                        (get-char-code-property char 'name)))))
+                        (char-to-name char)))))
      domain)
     ;; Does IDNA allow it?
     (unless (puny-highly-restrictive-domain-p domain)

lisp/simple.el

@@ -1827,8 +1827,7 @@ in *Help* buffer.  See also the command `describe-char'."
   (interactive "P")
   (let* ((char (following-char))
          (char-name (and what-cursor-show-names
-                         (or (get-char-code-property char 'name)
-                             (get-char-code-property char 'old-name))))
+                         (char-to-name char)))
          (char-name-fmt (if char-name
                             (format ", %s" char-name)
                           ""))