[Fix] Use prometheusScraping.port variable and honor prometheusScraping.enabled

[sporqist]

Problem: Setting a custom value for prometheusScraping.port in values.yaml has no effect, as the variable isn't actually being used in the port definition in chat-deployment.yaml.

Solution: Add the variable to port definitions in chat-deployment.yaml and fence it so the port only gets defined when prometheusScraping.enabled is true.

[CLAassistant]

All committers have signed the CLA.

[sporqist]

I accidentally made all the changes in my forks main branch. Gonna move this to a separate branch and open another pr.

[sporqist]

#47