[VS Code] Cycle Through Code Suggestions

MVC Proposal

In VS Code, use the existing Code Suggestions UI to show multiple suggestions and allow users to cycle through the suggestions. This will only apply to code completion.

Under Experiment/BETA in VS Code:

1. Start with code completion (currently using code-gecko) and use candidateCount as proposed.
2. Add telemetry to measure the effects of the feature, usage, and latency.

---

Open Questions (see )

1. What model modifications would we need to do to handle a collection of code suggestions, ensuring that it can support storing and managing multiple suggestions efficiently?
2. Should we limit the number of suggestions users can cycle through?
3. How would this impact our latency metrics?
4. How would this affect how we do caching?
5. Can we implement telemetry to track which suggestion is accepted (initially shown vs. second or third)?