add vanity mascot for upcoming fork to status bar (#5761)

To simplify supporting "am I ready for the fork" requests, add a simple
marker to the default status bar that indicates readiness by displaying
the fork's corresponding mascot. This is the same one that is also
displayed during the actual fork transition, so does not introduce
new dependencies. It also only shows in default status bar, not in logs.

beacon_chain/nimbus_beacon_node.nim

@@ -132,6 +132,19 @@ func getVanityLogs(stdoutKind: StdoutLogKind): VanityLogs =
       onUpgradeToDeneb:
         (proc() = notice "🐟 Proto-Danksharding is ON 🐟"))
 
+func getVanityMascot(consensusFork: ConsensusFork): string =
+  case consensusFork
+  of ConsensusFork.Deneb:
+    "🐟"
+  of ConsensusFork.Capella:
+    "🦉"
+  of ConsensusFork.Bellatrix:
+    "🐼"
+  of ConsensusFork.Altair:
+    "✨"
+  of ConsensusFork.Phase0:
+    "🦏"
+
 proc loadChainDag(
     config: BeaconNodeConf,
     cfg: RuntimeConfig,
@@ -1473,7 +1486,8 @@ proc onSlotEnd(node: BeaconNode, slot: Slot) {.async.} =
 
   await node.updateGossipStatus(slot + 1)
 
-func formatNextConsensusFork(node: BeaconNode): Opt[string] =
+func formatNextConsensusFork(
+    node: BeaconNode, withVanityArt = false): Opt[string] =
   let consensusFork =
     node.dag.cfg.consensusForkAtEpoch(node.dag.head.slot.epoch)
   if consensusFork == ConsensusFork.high:
@@ -1483,7 +1497,9 @@ func formatNextConsensusFork(node: BeaconNode): Opt[string] =
     nextForkEpoch = node.dag.cfg.consensusForkEpoch(nextConsensusFork)
   if nextForkEpoch == FAR_FUTURE_EPOCH:
     return Opt.none(string)
-  Opt.some($nextConsensusFork & ":" & $nextForkEpoch)
+  Opt.some(
+    (if withVanityArt: nextConsensusFork.getVanityMascot & " " else: "") &
+    $nextConsensusFork & ":" & $nextForkEpoch)
 
 func syncStatus(node: BeaconNode, wallSlot: Slot): string =
   let optimistic_head = not node.dag.head.executionValid
@@ -1970,7 +1986,8 @@ when not defined(windows):
         formatGwei(node.attachedValidatorBalanceTotal)
 
       of "next_consensus_fork":
-        let nextConsensusForkDescription = node.formatNextConsensusFork()
+        let nextConsensusForkDescription =
+          node.formatNextConsensusFork(withVanityArt = true)
         if nextConsensusForkDescription.isNone:
           ""
         else: