Fix clean command suggestion when using non-default port for remote targets

````
$ btrbk --version
btrbk command line client, version 0.32.6
````

````
$ sudo -u btrbk btrbk resume --progress
WARNING: Target subvolume "myhost.dyndns.com[1234]:/mnt/backup-system/myhost/root.20230913T1600" exists, but is not a receive target of "/mnt/btrfs/@snapshots/btrbk/root.20230913T1600"
WARNING: Please delete stray subvolumes: "btrbk clean myhost.dyndns.com[1234]:/mnt/backup-system/myhost"
WARNING: Skipping backup of: /mnt/btrfs/@snapshots/btrbk/root.20230913T1600
Creating backup: myhost.dyndns.com[1234]:/mnt/backup-system/myhost/root.20230914T1450
...
>>> myhost.dyndns.com[1234]:/mnt/backup-data/myhost/data.20230924T1500
>>> myhost.dyndns.com[1234]:/mnt/backup-data/myhost/data.20230925T1700
>>> myhost.dyndns.com[1234]:/mnt/backup-data/myhost/data.20230926T1300
>>> myhost.dyndns.com[1234]:/mnt/backup-data/myhost/data.20230926T1400
>>> myhost.dyndns.com[1234]:/mnt/backup-data/myhost/data.20230926T1505
>>> myhost.dyndns.com[1234]:/mnt/backup-data/myhost/data.20230926T1533
>>> myhost.dyndns.com[1234]:/mnt/backup-data/myhost/data.20230926T1600

NOTE: Some errors occurred, which may result in missing backups!
Please check warning and error messages above.
Please delete stray subvolumes: "btrbk clean myhost.dyndns.com[1234]:/mnt/backup-system/myhost"
Please delete stray subvolumes: "btrbk clean myhost.dyndns.com[1234]:/mnt/backup-data/myhost"
````

The suggested command `btrbk clean myhost.dyndns.com[1234]:/mnt/backup-data/myhost` doesn't work.

````
sudo -u btrbk btrbk clean myhost.dyndns.com\[1234\]:/mnt/backup-system/myhost
ERROR: Filter argument "myhost.dyndns.com[1234]:/mnt/backup-system/myhost" does not match any volume, subvolume, target or group declaration
````

The command has to be `btrbk clean myhost.dyndns.com:1234/mnt/backup-system/icarus`

Maybe it makes sense to change the output of the subvolume names too to the "real" name/location?
````
>>> myhost.dyndns.com:1234/mnt/backup-data/myhost/data.20230926T1300
````

Start by tracing the btrbk clean command and the warning output generated by resume for remote targets with a non-default port. Reproduce the reported myhost.dyndns.com[1234] case and verify that the suggested clean command is accepted and that displayed remote paths use one consistent location format.

Written by the indexing model from the issue text.