Improvements for bandwidth configuration of network offering

##### ISSUE TYPE

* Improvement Request

##### COMPONENT NAME

Network offerings

##### CLOUDSTACK VERSION
~~~
4.20.0.0
~~~

##### OS / ENVIRONMENT

Ubuntu 22.04 (if relevant)
mysql 8

##### SUMMARY

All default network offerings are shown in UI as having 200Mb/s network rate. I created my own network offering without specifying network rate, and it's also shown in UI as having 200Mb/s.
Then I checked database and found that no network offering has a positive value in `network_offerings` table. All System ones have 0, while all other (default) ones have NULL.
But then, when I checked xml of Virtual router (I use isolated network with nat, if relevant again), I found this definition on my external network
```

```
That is 25Mb/s.

After I set network rate to 65K in my network offering, it become consistent at least between DB and CloudStack UI, VR then got
```




```
And another, minor, issue on the way - mysql defines the field as smallint:
`nw_rate smallint unsigned DEFAULT NULL COMMENT 'network rate throttle mbits/s'`
that does not allow values larger than 65K (worth adding an info on this to UI of creating network offering).
Modern networks can work on a larger speeds (e.g. 800Gb/s). Besides would be nice to be able not to limit it at all.

Thanks,
Alex.

Commencez par retracer comment les offres réseau sont affichées dans l’UI et comment network_offerings.nw_rate est stocké et interprété. Comparez ces valeurs avec la bande passante émise dans le XML de virtual-router, puis définissez comme terminé le traitement cohérent des valeurs non définies et des valeurs de débit élevé, avec notamment des indications claires dans l’UI sur les limites ou la bande passante illimitée.

Rédigé par le modèle d'indexation à partir du texte de l'issue.