Implement `Power up` part of hive power management

Requires:

1. !298 (merged) (to change the inputs to the new)

clive/__private/ui/operations/hive_power_management/common_hive_power/additional_info_widgets.py

@@ -66,13 +66,19 @@ class WithdrawalInfo(Vertical, CliveWidget):
         )
 
     def _get_next_withdrawal_date(self, content: HivePowerData) -> str:
-        return humanize_datetime(content.next_vesting_withdrawal)
+        if self._provider.is_content_set:
+            return humanize_datetime(content.next_vesting_withdrawal)
+        return "loading..."
 
     def _get_to_withdraw_hp(self, content: HivePowerData) -> str:
-        return f"{Asset.pretty_amount(content.to_withdraw.hp_balance)} HP"
+        if self._provider.is_content_set:
+            return f"{Asset.pretty_amount(content.to_withdraw.hp_balance)} HP"
+        return "loading..."
 
     def _get_to_withdraw_vests(self, content: HivePowerData) -> str:
-        return f"{Asset.pretty_amount(content.to_withdraw.vests_balance)} VESTS"
+        if self._provider.is_content_set:
+            return f"{Asset.pretty_amount(content.to_withdraw.vests_balance)} VESTS"
+        return "loading..."
 
 
 class APR(DynamicLabel):