We should reserve a port for the Prometheus exporter

[thaiphv]

Is your feature request related to a problem? Please describe.
We haven't reserved a port for the Prometheus exporter and currently use a default port that is reserved for the node_exporter. We should update https://github.com/prometheus/prometheus/wiki/Default-port-allocations and reserve the next available port for the Rocket.Chat Prometheus exporter.

Describe the solution you'd like
I will update https://github.com/prometheus/prometheus/wiki/Default-port-allocations and reserve the next available port, which is 9458, for the Rocket.Chat Prometheus exporter. And then submit a pull request that sets the default port to this value. This will be a broken change but I believe if someone actually use Prometheus for monitoring, they have to set the port to some other value than 9100. This setting is available in 0.66.0.

Describe alternatives you've considered
N/A

Additional context
N/A