Remove tokio dependency

[mineichen]

• Remove tokio/async_stream/tokio_stream dependencies and use lighter futures_util/pin-project-lite instead
• Unify streaming apis with a Lines adapter
  • Most of them had problems, if one Bytes would contain multiple lines, which could happen everywhere
• use try_next() instead of .next() to improve readability
• Share common code in streaming and non-streaming methods

Breaking:

• Change ChatMessageResponse to return OllamaError instead of ()
• Remove GenerationResponseStreamChunks and stream all items independently
• Chat returns Error if one occurs... The Caller can still filter errors out and continue
• Non-Streaming consistenly returns Reqwest-Error instead of OllamaError::Other if error-text cannot be gathered from response (sometimes it was res.text().await?, sometimes res.text().await.unwrap_or_else(|e| e.to_string()),)

Functionaity should stay almost the same. Sorry for the big chunk... What i'd like to send separately later:

• Allow WASM-Build (currently reqwest::bytes_stream() is !Send)
• Remove all stream properties from the requests and send them with WithSendField-heper
• Introdce pub(crate) Ollama::send_request() to remove duplication of building request with common stuff