distro/rhel86: add RHEL 8.5 variant

Define the distribution strings for RHEL 8.5 in distro/rhel86 and add
constructors.  Remove the old 8.5 from the distro registry and use the
new constructors.

Composer can now build RHEL 8.5 image-installer on aarch64, which wasn't
supported before.

RHEL 8.5 manifests have changed to minimise the differences from 8.6.
Some changes are fixes made in 8.6 but never backported to 8.5 because
of our (older) policy of not changing definitions after the release of a
distro.
Other changes are non-functional (e.g., stage or package order).

See the list below for the source of each change.

Manifest changes:
- Stage order changed for org.osbuild.systemd-logind and
  org.osbuild.rhsm.
- org.osbuild.grub2 options: config.default = "saved"
  Reverted 111cd8871f
- Partition sizes: RHEL 8.5 had extra arbitrarily sized padding for the
  header.  Now all partitions are sized to fit headers exactly.
  Original change at b7abef54e8.
- SELinux set to permissive in Anaconda.  This was changed in RHEL 8.6
  and 9.0 but never backported to 8.5.
  See a7fbe916b7.
- Installer isolevel set to 3.  Like above, this was changed in
  8.6 and 9.0.
  Original change at d8d161480e.
- Specify a remote for edge deployments.
  Original change at b18b4e80a0.

test/data/manifests/rhel_85-aarch64-edge_installer_with_users-boot.json

@@ -3437,8 +3437,6 @@
                 "systemd-initrd",
                 "modsign",
                 "nss-softokn",
-                "rdma",
-                "rngd",
                 "i18n",
                 "convertfs",
                 "network-manager",
@@ -3458,14 +3456,8 @@
                 "livenet",
                 "lvm",
                 "mdraid",
-                "multipath",
                 "qemu",
                 "qemu-net",
-                "fcoe",
-                "fcoe-uefi",
-                "iscsi",
-                "lunmask",
-                "nfs",
                 "resume",
                 "rootfs-block",
                 "terminfo",
@@ -3478,12 +3470,26 @@
                 "img-lib",
                 "shutdown",
                 "uefi-lib",
-                "anaconda"
+                "anaconda",
+                "rdma",
+                "rngd",
+                "multipath",
+                "fcoe",
+                "fcoe-uefi",
+                "iscsi",
+                "lunmask",
+                "nfs"
               ],
               "install": [
                 "/.buildstamp"
               ]
             }
+          },
+          {
+            "type": "org.osbuild.selinux.config",
+            "options": {
+              "state": "permissive"
+            }
           }
         ]
       },
@@ -3594,7 +3600,8 @@
               "filename": "installer.iso",
               "volid": "RHEL-8-5-0-BaseOS-aarch64",
               "sysid": "LINUX",
-              "efi": "images/efiboot.img"
+              "efi": "images/efiboot.img",
+              "isolevel": 3
             }
           },
           {