fix(utils): log exceptions on stake and DRep operations

Updated `testnet_cleanup.py` to use `LOGGER.exception` instead of
`LOGGER.error` for better error traceability when re-registering or
deregistering stake addresses and retiring DReps.

Changes:
- Replaced `LOGGER.error` with `LOGGER.exception` in three functions:
  `reregister_stake_addr`, `deregister_stake_addr`, and `retire_drep`.

This improves debugging by including stack traces in the logs.

Author: mkoura

cardano_node_tests/utils/testnet_cleanup.py

@@ -76,7 +76,7 @@ def reregister_stake_addr(
                 deposit=rereg_deposit,
             )
         except clusterlib.CLIError:
-            LOGGER.error(f"Failed to re-register stake address '{stake_addr.address}'")  # noqa: TRY400
+            LOGGER.exception(f"Failed to re-register stake address '{stake_addr.address}'")
         else:
             LOGGER.debug(f"Re-registered stake address '{stake_addr.address}'")
             stake_addr_info = cluster_obj.g_query.get_stake_addr_info(stake_addr.address)
@@ -121,7 +121,7 @@ def deregister_stake_addr(
             deposit=-deposit_amt,
         )
     except clusterlib.CLIError:
-        LOGGER.error(f"Failed to deregister stake address '{stake_addr.address}'")  # noqa: TRY400
+        LOGGER.exception(f"Failed to deregister stake address '{stake_addr.address}'")
     else:
         LOGGER.debug(f"Deregistered stake address '{stake_addr.address}'")
 
@@ -152,7 +152,7 @@ def retire_drep(
             deposit=-deposit_amt,
         )
     except clusterlib.CLIError:
-        LOGGER.error(f"Failed to retire a DRep '{name_template}'")  # noqa: TRY400
+        LOGGER.exception(f"Failed to retire a DRep '{name_template}'")
     else:
         LOGGER.debug(f"Retired a DRep '{name_template}'")