.Net: Decide on the metadata names for the newAzureOpenAIChatCompletionService

[SergeyMenshykh]

Metadata names have been changed in Azure.OpenAI SDK v2. It needs to be decided whether we propagate those changes to the SK users or we keep the old names where it's possible.

See the issue - #7053 for more details.

[SergeyMenshykh]

It was decided to propagate all the metadata from the underlying library as is, with no changes, transformations, or abstractions. Later, some common metadata can be promoted to abstraction.