Add plumbing for PeerDAS supernodes (#5050, #5409, #5570, #5966) (#6216)

* Add plumbing for peerdas supernodes (#5050, #5409, #5570, #5966)
- add cli option `--subscribe-to-all-data-columns`
- add custody subnet count to ENR, only if PeerDAS is scheduled
- subscribe to data column topics, only if PeerDAS is scheduled

Co-authored-by: Jacob Kaufmann <jacobkaufmann18@gmail.com>

* Merge branch 'unstable' into das-supernode

* Update CLI docs.

* Merge branch 'unstable' into das-supernode

* Fix fork epoch comparison with `FAR_FUTURE_EPOCH`.

* Merge branch 'unstable' into das-supernode

* Hide `--subscribe-all-data-column-subnets` flag and update help.

* Fix docs only

* Merge branch 'unstable' into das-supernode

beacon_node/src/cli.rs

@@ -54,6 +54,18 @@ pub fn cli_app() -> Command {
         /*
          * Network parameters.
          */
+        .arg(
+            Arg::new("subscribe-all-data-column-subnets")
+                .long("subscribe-all-data-column-subnets")
+                .action(ArgAction::SetTrue)
+                .help_heading(FLAG_HEADER)
+                .help("Subscribe to all data column subnets and participate in data custody for \
+                        all columns. This will also advertise the beacon node as being long-lived \
+                        subscribed to all data column subnets. \
+                        NOTE: this is an experimental flag and may change any time without notice!")
+                .display_order(0)
+                .hide(true)
+        )
         .arg(
             Arg::new("subscribe-all-subnets")
                 .long("subscribe-all-subnets")