Implement `Power up` part of hive power management

Requires:

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

clive/__private/cli/commands/process/process_proxy_clear.py

+from __future__ import annotations
+
+from dataclasses import dataclass
+
+from clive.__private.cli.commands.abc.operation_command import OperationCommand
+from schemas.operations import AccountWitnessProxyOperation
+
+
+@dataclass(kw_only=True)
+class ProcessProxyClear(OperationCommand):
+    account_name: str
+
+    async def _create_operation(self) -> AccountWitnessProxyOperation:
+        return AccountWitnessProxyOperation(
+            account=self.account_name,
+            proxy="",
+        )