Revert "Add key management system" (978f869b99) & later commits

The patch needs test cases, reorganization, and cfbot testing.
Technically reverts commits 5c31afc49d..e35b2bad1a (exclusive/inclusive)
and 08db7c63f3..ccbe34139b.

Reported-by: Tom Lane, Michael Paquier

Discussion: https://postgr.es/m/E1ktAAG-0002V2-VB@gemulon.postgresql.org

doc/src/sgml/ref/pgupgrade.sgml

@@ -167,15 +167,6 @@ PostgreSQL documentation
       </para></listitem>
      </varlistentry>
 
-     <varlistentry>
-      <term><option>-R</option></term>
-      <term><option>--authprompt</option></term>
-      <listitem><para>allows <option>ssl_passphrase_command</option> or
-      <option>cluster_key_command</option> to prompt for a passphrase
-      or PIN.
-      </para></listitem>
-     </varlistentry>
-
      <varlistentry>
       <term><option>-s</option> <replaceable>dir</replaceable></term>
       <term><option>--socketdir=</option><replaceable>dir</replaceable></term>
@@ -318,9 +309,7 @@ make prefix=/usr/local/pgsql.new install
      Again, use compatible <command>initdb</command>
      flags that match the old cluster. Many
      prebuilt installers do this step automatically. There is no need to
-     start the new cluster.  If upgrading a cluster that uses
-     cluster file encryption, the <command>initdb</command> option
-     <option>--copy-encryption-keys</option> must be specified.
+     start the new cluster.
     </para>
    </step>
 
@@ -849,13 +838,6 @@ psql --username=postgres --file=script.sql postgres
    is down.
   </para>
 
-  <para>
-   If the old cluster uses file encryption, the new cluster must use
-   the same keys, so <command>pg_upgrade</command> copies them to the
-   new cluster.  It is necessary to initialize the new cluster with
-   the same <varname>cluster_key_command</varname> and the same
-   file encryption key length.
-  </para>
  </refsect1>
 
  <refsect1>