Add AzureOpenAIGenerator

[mathislucka]

Is your feature request related to a problem? Please describe.
We should support Azure Open AI services. It's a widely used service that is particularly relevant for professional production use.

See also: deepset-ai/haystack#6620

Describe the solution you'd like
Similar to 1.x we need a component that supports OpenAI models hosted on Azure.

Describe alternatives you've considered
None

[masci]

@vblagoje Can we close this now that we merged deepset-ai/haystack#6648 ?

[vblagoje]

Yes, completed with deepset-ai/haystack#6648 Closing

[vblagoje]

@masci @mathislucka we decided to keep Azure Generators inside the haystack project codebase as it doesn't introduce any new dependencies.