feat(client): support new unified Azure URL scheme

[jpalvarezl]

Proposed changes:

• Adding necessary changes to support /openai/v1 Azure endpoints (referred to as "unified", as in "unified with the OpenAI schema", meaning that the model/deployment is not a path parameter of the request URL and api-version is optional).
• Currently the services still requires an api-version query parameter with the value of preview, but in the future the omission of this query parameter will result in the service defaulting to v1 meaning "latest".
• Added unit tests
• Added samples and updated old ones
• Added azureUrlPathMode enum as a manual switch between the old behaviour of adding deployment name to the URL and the OpenAI unified URL schema. (Added as an enum to future proof)

Azure URL handling changes

• Added support for new hosts ("services.ai.azure.com") for unified Azure endpoints. (no longer injecting model name in the path. api-version is optional)
• Other hosts flagged as Azure, are treated the old way (deployment or model name is added to the path. api-version is required)

For a more detailed discussion on the spec please refer to this message in the original PR thread.

cc: @srnagar and @trrwilson

[jpalvarezl]

Updated the azureLegacyPaths: Boolean toggle to be azureUrlPathMode: AzureUrlPathMode enum. Just giving a heads up to @trrwilson and @srnagar, since this deviates a bit from the original proposal (mainly concerned about objections to the naming, since everyone was already agreeing as having this as an enum instead).