Remove "bind -k" terminfo key names, update "bind --key-names"

I don't think there's a relevant terminal where the "bind -k" notation is
still needed. The remaining reason to keep it is backwards compatibility.

But "bind -k" is already subtly broken on terminals that implement either
of modifyOtherKeys, application keypad mode or the kitty keyboard protocol,
since those alter the byte sequences (see #11278).

Having it randomly not work might do more harm than good. Remove it.

This is meant go into 4.1, which means that users who switch back and forth
between 4.1 and 4.0 can already use the new notation.

If someone wants to use the bind config for a wider range of versions they
could use "bind -k 2>/dev/null" etc.

While at it, use the new key names in "bind --key-names", and sort it like
we do in "bind --function-names".

Closes #11342

doc_src/cmds/bind.rst

@@ -11,6 +11,7 @@ Synopsis
     bind [(-M | --mode) MODE] [--preset] [--user] [KEYS]
     bind [-a | --all] [--preset] [--user]
     bind (-f | --function-names)
+    bind (-K | --key-names)
     bind (-L | --list-modes)
     bind (-e | --erase) [(-M | --mode) MODE] [--preset] [--user] [-a | --all] | KEYS ...
 
@@ -72,6 +73,9 @@ The following options are available:
 **-f** or **--function-names**
     Display a list of available input functions
 
+-**-K** or **--key-names**
+    Display a list of available named keys such as ``backspace``.
+
 **-L** or **--list-modes**
     Display a list of defined bind modes
 
@@ -102,12 +106,6 @@ The following options are available:
 **-s** or **--silent**
     Silences some of the error messages, including for unknown key names and unbound sequences.
 
-**-k KEY_NAME** or **--key KEY_NAME**
-    This looks up KEY_NAME in terminfo and binds that sequence instead of a key that fish would decode.
-    To view a list of the terminfo keys fish knows about, use ``bind --key-names`` or ``bind -K``.
-    This is deprecated and provided for compatibility with older fish versions. You should bind the keys directly.
-    Instead of ``bind -k sright`` use ``bind shift-right``, instead of ``bind -k nul`` use ``bind ctrl-space`` and so on.
-
 **-h** or **--help**
     Displays help about using this command.