Find a consistent pattern for LLM span names

[lmolkova]

We probably need to standardize operation name (as attribute) - e.g. openai object like "chat.completion" or "embedding" and use the operation name inside the span name as well.

[sudivate]

Hi @lmolkova, I have started working on this PR, can you please add me to the project and assign this to me.

Should this be gen_ai.operation.name with below possible operations name

• chat.completions
• embeddings
• speech.generations
• audio.transcriptions
• audio.translations
• image.generations

https://github.com/sudivate/semantic-conventions/blob/0550e6fa8ccaa382c26ab8f4cd5b957f65c5aed0/model/registry/gen-ai.yaml#L50