Change default postgresql logs files naming

## Steps to reproduce

1. Deploy any version of the charm

## Expected behavior
Logs files name with a better operator visibility.

## Actual behavior

Current default is
```
log_filename: 'postgresql-%w_%H%M.log'
```
That's allowing a weekly rotation which we don't really want by default anyway (it's really short on production if there isn't any external logging involved).
Files are really hard to walk by this way, I would prefer a consolidated daily or, if you have a strong opinion about this, hourly, log rotation.
Logrotate configuration should take care of the pruning of old log files and also help with space with compression mechanism.

## Versions

Operating system: Ubuntu 22.04.5 LTS

Juju CLI: 3.6.2-ubuntu-amd64

Juju agent: 3.1.8

Charm revision: 14/candidate rev 331

## Additional context
Stumbled across the lack of visibility of obvious issues with max_connections because of the log file naming.

I get that a mere `cat postgresql-%w* | less` give me the same result but that seems an unnecessary step.
What I'm more worried about is the weekly log overwrite it implies, given not everybody (ahem) has logging export and storage and that it can cause a really weird mix of logs like this:
```
$ sudo ls -lart /var/snap/charmed-postgresql/common/var/log/postgresql/postgresql-1_063*
-rw------- 1 snap_daemon snap_daemon 6815 Jan 13 06:34 /var/snap/charmed-postgresql/common/var/log/postgresql/postgresql-1_0634.log
-rw------- 1 snap_daemon snap_daemon 6235 Jan 13 06:35 /var/snap/charmed-postgresql/common/var/log/postgresql/postgresql-1_0635.log
-rw------- 1 snap_daemon snap_daemon 6380 Jan 13 06:36 /var/snap/charmed-postgresql/common/var/log/postgresql/postgresql-1_0636.log
-rw------- 1 snap_daemon snap_daemon 6525 Jan 13 06:37 /var/snap/charmed-postgresql/common/var/log/postgresql/postgresql-1_0637.log
-rw------- 1 snap_daemon snap_daemon 6380 Jan 13 06:38 /var/snap/charmed-postgresql/common/var/log/postgresql/postgresql-1_0638.log
-rw------- 1 snap_daemon snap_daemon 6525 Jan 20 06:30 /var/snap/charmed-postgresql/common/var/log/postgresql/postgresql-1_0630.log
-rw------- 1 snap_daemon snap_daemon 6525 Jan 20 06:31 /var/snap/charmed-postgresql/common/var/log/postgresql/postgresql-1_0631.log
-rw------- 1 snap_daemon snap_daemon 3770 Jan 20 06:32 /var/snap/charmed-postgresql/common/var/log/postgresql/postgresql-1_0632.log
-rw------- 1 snap_daemon snap_daemon 17255 Jan 20 06:38 /var/snap/charmed-postgresql/common/var/log/postgresql/postgresql-1_0633.log
-rw------- 1 snap_daemon snap_daemon 5800 Jan 20 06:39 /var/snap/charmed-postgresql/common/var/log/postgresql/postgresql-1_0639.log
```
You can see here that we have a mix of logs for this week, and on the few minutes were no logs were written, still the logs from the previous week.