Allow for custom nginx configuration for streams in WebUI

Is your feature request related to a problem? Please describe.

NPM streams does not have an 'advanced' tab for custom nginx configuration similar to nginx proxies. There are some use cases where this would be handy. See here:

https://github.com/NginxProxyManager/nginx-proxy-manager/issues/3619

Describe the solution you'd like

Allow for nginx custom configuration on streams through the WebUI

Describe alternatives you've considered

Manually editing the files which could break NPM's relationship to the configuration file based upon the stream template
https://github.com/NginxProxyManager/nginx-proxy-manager/blob/d40f9e06fc25acbf6906663edcef462a1a902cdf/backend/templates/stream.conf

EDIT: I just found the advanced documentation which says to do what I mentioned above, and this will technically allow for custom configs to not break NPM's generation of configs

Additional context

https://github.com/NginxProxyManager/nginx-proxy-manager/issues/3619

Start by reading backend/templates/stream.conf and the related issue 3619, then trace how stream settings are exposed in the WebUI and persisted. Done means users can enter custom nginx configuration for a stream through the WebUI without breaking generated stream configuration.