Support generic /chat/completions and /completions route for azure proxy + configs call

[VisargD]

Currently, even for proxy calls with configs, user needs to send the actual azure config in the url itself. But when you pass a config in proxy call, it overwrites the url with whats written in config which causes confusion. Need to have a generic interface for proxy calls which just accepts type (chat/text) and then takes the provider options from config itself.

Current proxy url for azure: {{host}}/v1/proxy/{{RESOURCE}}.openai.azure.com/openai/deployments/{{DEPLOYMENT_ID}}/chat/completions?api-version={{API_VERSION}}

The problem with this implementation is that when you pass a config with the API call, it overwrites whatever is written in url which causes confusion.

New implementation for config enabled proxy calls:
{{host}}/v1/proxy/chat/completions
{{host}}/v1/proxy/completions

NOTE: The old implementation is still applicable if users are making simple proxy calls without config.