.Net: MistralAI Connector

[markwallace-microsoft]

### Tasks
- [x] Connector and unit test projects initial check-in
- [x] Chat completion support
- [x] Embedding support
- [x] Streaming chat completion support
- [x] Function calling support
- [x] Streaming function calling support
- [x] Refactor to use the SSE Parser
- [x] Switch to using new Function Call Content classes
- [x] Add support for function calling filters
- [x] Test function calling using the "any" tool choice
- [ ] Test function calling with multiple tool calls
- [x] Text terminating auto function calling and then continuing the chat history
- [ ] Test coverage and syntax samples
- [ ] Switch to Function Calling abstractions
- [ ] Bug bash

[matthewbolanos]

Closing since everything is done except for moving to the function calling abstractions which has its own issue #6555